The MFM or Shared Wife Fantasy

This guide is primarily written for beginners, mature in their views of sexuality, who are considering this next step.  It also includes alternatives for those couples who don't feel comfortable making the fantasy a reality at this time.

You'll see that a sensible GO SLOW approach is suggested.  Why?  Because it allows the couple to maintain a sense of control as they explore their own deepest desires and those of their partners.  In addition, it provides the opportunity to stop at any time if either partner feels uncomfortable. 
 
 

Before we begin...

An important clarification must be made.  This is not swinging.  It is not "open marriage" which is simply another word for swinging.   The author neither condones or supports the swinging lifestyle.  Bringing the MFM or shared wife fantasies to life does not lead to swinging - at least not for me or anyone that has a sincere interest in this fantasy.  Please look elsewhere if that is your interest.

A trusting relationship where a couple supports and encourages the women's sexual experimentation with another male partner, but maintains a strong emotional bond with one another.

MFM sexual experimentation may take several forms from rather benign flirtation to exhibitionism.  These moderately erotic sexual activities are discussed in a later chapter.  The bulk of this guide refers to a relationship that eventually leads to physical sex. 

It is often said that this fantasy taps into the way men and women are wired.  What is the driving force behind this desire for the man?  For the women?  Is It normal?  Read on.

To consider an MFM experience, whether is it serious flirtation or much more, provides a new dimension in sexuality. For mature couples, it can be both positive and mutually satisfying, with a little planning and forethought.  The feeling of sexual power and confidence, by enticing two males into bed can be a huge turn on.  As a rule, women are capable of outlasting any one man, and with a second partner she may be able to reach a previously unobtainable sexual high.  The result is more often than not "memorable sex" that you both think fondly of and recall from time to time.

Of course, any major change in our sex lives can be cause for concern.  It is with a certain amount of fear that most women begin their sex life or try a sex toy with their partner for the first time.  But with each chance taken, new pleasures are often realized.  All couples have initial feelings of intrepedation with MFM encounters, but those anxious moments fade away and are replaced by sexual joy.

SUGGESTED LITERATURE
For more information on women's sexuality, I would suggest any of the following:

The Ethical Slut: A Guide to Infinite Sexual Possibilities
by Dossie Easton and Catherine Liszt Greenery Press

Turn Ons: Pleasing Yourself While Pleasing Your Lover
by Lonnie Barbach, Ph.D. Plume

Best Women's Erotica
by Marcy Sheiner, Cleis Press 

Women on Top: How Real Life Has Changed Women's Sexual Fantasies
by Nancy Friday Pocket Books

The Erotic Mind : Unlocking the Inner Sources of Sexual Passion and Fulfillment
by Dr. Jack Morin

Exhibitionism for the Shy : Show Off, Dress Up and Talk Hot
by Carol Queen

The Erotic Edge: 22 Erotic Stories for Couples
by Lonnie Barbach, Ph.D.  Plume

Cyborgasm (Audio Cassette)
by Lisa Palac 

MEN'S MOTIVATION

The desire for a man to see his partner sexually experimenting with another is an "awakening" for him as his sexuality matures.  This common fantasy comes about, perhaps unexpectedly, for many men and women as they age.  Young men in their teens and early twenties do not typically have this desire.  It seems to develop after a decade or two of sexual experience and can be a source of unbridled eroticism.

There are a variety of reasons men may encourage their wives to sexually engage other men.  If you're looking for a simple explanation, I have none to offer but I might suggest you read "Brain Sex, (Moir & Jessel, 1993)"  or Sex on the Brain : The Biological Differences Between Men and Women (Blum, 1998) which contains bits and pieces of what makes men and women tick.  There have been recent television specials on the Discovery channel such as "Brain Sex" that offer additional clues.

His desire to encourage his partner to explore sex with another man is driven by many complex and intertwined reasons that even he may have difficulty verbalizing.  The more common themes are explored here:

• Unconditional love
• Reliving past sex
• New sex
• Pure lust sex
• Competition with other males
• Cum fantasy
• Sexual Control
• Husband humiliation
• Wife humiliation

  
  Unconditional Love:  In a trusting and loving relationship the man encourages her to have a pleasurable erotic sexual experience with another partner.  He knows she will enjoy it immensely if she has his support.  He may feel that she was cheated out of sexual experimentation that he engaged in as a young man prior to the current relationship.  Essentially, it is an act of love, where he gives her something very special.

  Reliving past sex:  Most couples at some point explore her past sexual relationships through fantasy.  She finds that her sexual history is a powerful source of eroticism for him.  Many men discover their own desire for a shared wife experience in this manner.

  New Sex:  Sex with a new partner is often very highly charged and perhaps biological in nature.  For nearly all couples, it is fondly remembered.  Bringing another man into your relationship can result in a similar level of intensity that you experienced when you first shared one another - maybe greater.  :-)  A woman who has been in a long term monogamous relationship will often behave as if she has been starved for sex when a new partner begins to engage in adult play with her.   For a man, most of whom are very visual, the site of another male playing with his partner may cause uncontrollable arousal. The many "shared wife with another man" pictures posted on the web and related stories are strong evidence of this common and perfectly normal fantasy.  Check out the Toy Box (couples section) or the many forums on this topic on Yahoo or Excite.

  Pure lust sex:  The sex a couple has over the years can be wild and passionate, but it is not exactly the same as the kind of sex she would have with someone she is not emotionally involved with.  Pure lust sex has a different dimension.  He wants to see that "desire for a stud" look in her eyes, driven by female hormones and animal instinct.

  Competition:  Male competition allows him to measure his ability to stimulate his mate against another male.  A darker side of this fantasy is impregnation competition.  Men are evolutionary designed for this as a penis is shaped to pull out the semen of another and replace it with his own.  I do not promote or condone impregnation.  Another area of competition is penis size.  More on that later.

  Cum fantasy:  As part of nearly all pair bonding relationships in the mammal world, males want sole access to their mate's sexual zones, and specifically for the deposition of semen.  This is a sacred right for any couple.  Placing Sexually Transmitted Diseases aside for a moment, the idea of another male given this same access and opportunity may be very erotic for him.  The sight, smell or feel of another man's cum in her mouth or vagina is taboo and also an erotic fantasy.

  Husband humiliation:  This one I can not relate to personally.  It seems that some men want their partner to exhibit control over them, choosing to deny them sexual satisfaction by finding another sexual source.  This is known as cuckolding and not explored in this guide.

  Wife humiliation:  Another one I don't relate to personally.  Some men like the feeling of power they have ordering their partner to submit to sex with another man.

I'm sure there are other motivations, but the group listed here represent the mainstream reasons men suggest to their partners to engage in sex with another man.  If the male readers can relate to any or all of the above, you are perfectly normal as millions of other guys have these same fantasies.
 
 

WOMEN'S MOTIVATIONSome women have a reoccurring MFM fantasy.   Others have not given it much thought until asked about it.  Perhaps you have been directed here by your mate to learn more? 

Woman reading this who have not explored the topic of sexual play another man should try bringing the subject up some time when your partner is aroused.  You may be pleasantly surprised by the result.  :-)  For those of you trying to understand why he wants to pursue this and what it would be like, I hope this will help you make an informed decision.

In the right circumstances, I've asked women what motivated them to seek sex outside of their relationship and this is what they've shared:

• "New sex" pleasures
• Pleasing her partner
• Guilt free lustful sex
• Sex with a more desirable partner
• Being ravished
• Need to validate her desirability
• Fulfilling missed sexual experiences
• Unconditional belonging
• Enjoying sex similar to that before being married
• Being with more than one man at a time

• • 
    "New sex" pleasures:  For men and women, sex with a new partner is in most cases very erotic.  It is likely she will have one of the most memorable sexual experiences in her life.

    Pleasing her partner:  Through the exploration of relationships with her previous lovers, she learns of his desire for her to engage in sexual play with a new partner.  She finds he is seriously turned on by the thought of this fantasy and finds his lustfulness associated with this topic equally arousing.  He wants to bring this fantasy to life more than anything and by granting his wish, she gives him something very special.

    Guilt free lustful sex:  Sex without the emotional baggage of a relationship can feel more heightened for her.   It can be a liberating experience for those women who have not yet tried it.  In an MFM adult play situation, she can concentrate totally on her pleasure, her desire and her needs.

    Sex with a more desirable partner:  No one man can satisfy a woman's erotic desires in every way.  In an MFM experience, she has the opportunity to select a mate that is different than her current lover.  He could be younger or maybe leaner or maybe from another part of the world.  If she has always had the hots for a guy with lots of muscles, this is her opportunity.

    Being ravished:  The thought of a man she hardly knows seeing her naked, aroused and unable to resist his advances is a female fantasy.  Her new partner is full of desire for her and is allowed to touch her everywhere and "take" her.

    Need to validate her desirability:  Some women need to know they are attractive and viewed as sensual.  No experience will validate her desirability more than attracting another partner for sexual play.  It can be a ego boost for her, especially if she has been having doubts about her ability to attract others.  Ask any 50 year old women if she feels more attractive after a shared wife experience with a younger stud and you'll get an affirmative response.

    Fulfilling missed sexual experiences:  She's lived an overly conservative life and now realizes she has missed out on the opportunity to sample sex with other men.  Now is her chance to experience a variety of partners.

    Unconditional belonging:   A deep sense of bonding where she feels owned by her partner.  This occurs when the husband/boyfriend, after making sure she is completely ready, invites another man to have her.  She is "his woman" and is given away.  Some couples experience a very strong emotional attachment as they look at one another while a new partner is intimately engaged with her.

    Enjoying sex similar to that before being married:  Perhaps she longs again for that freedom she had to sleep with whomever she wished.  (editorial note:  Most men can relate with this).

    Being with more than one man at a time:  It is not just guys who have the fantasy of being with two members of the opposite sex at once.  Some women find it arousing.

  
  This is by no means a complete list. Perhaps one of the female readers can elaborate on what I've written here.  Drop me an e-mail. (mfm@onebox.com)

• Have you explored the more moderately erotic sexual activities first?  There are several turn-ons that help to bring about sexual maturity.  These are discussed in the next section. 

• The fantasy has to become her fantasy.  In some cases, this is a difficult hurdle and is discussed in the next sections.  Men often fail to understand that turning this fantasy into reality for her is more of a journey, with several key steps along the way.

• She must be capable of having sex without emotional involvement.  This is relatively easy for a large percentage of men, but may be difficult for women.  Society dictates to women, from a young age that "where her body goes, so does her heart".  It is important that you talk about this issue up front so she can feel comfortable with sexual play without attachment.

• Age makes a difference for some.  Older couples, in their 30's and beyond are generally more comfortable with this type of adult play.  This is particularly true for women.

Women want respect, love and physical sex - usually in that order.  If you're preparing to discuss this seriously with your partner, this is a perfect time to work on your relationship.   Before you broach the subject directly, it is assumed you've already explored her sexual past and have bought toys that help explore sex with another partner.  There are countless ideas, but I've compiled a list of sexual experiences that encourage sexual maturity for both of you:

• Less sexually advanced:
  • Have her dress up in a sexy outfit such as tight jeans and blouse, then go to a secluded location such as a park.  Unbutton a few buttons on her blouse or jeans and take photographs of her in sexy poses.
  • Give your wife a gift certificate for a body massage and prearrange to have a man deliver the massage.
  • Read one of the books in the Women Readers section.
  • Role play.  Have her come into a bar and flirt with you, pick you up and take you home.
  • Have sex in risky places where there is a chance someone might see you.
  • Buy her a revealing dress.  Go somewhere you won't be known and dance the night away in front of others.
  • Have her dress provocatively, then go to a public place.  Watch other men watch her.

  
  More advanced:

  • If you're apart (e.g. business travel), call her when you've been away for several days and encourage her to act as if your fantasy has come true over the phone.
  • Place an ad in "Your Wife's Lovers" on the Dark Wanderer and encourage a man to have a cyber-sex relationship with your wife. 
  • Post a sexy picture of her, where her identity is not revealed on the net, then ask for comments and read them together.
  • Have a male masseuse come to the house and give your wife a body massage as a surprise.
  • Have her dress provocatively, then go out and expose her breasts or sexy behind to someone she knows or a stranger.
  • Take her dancing, sit apart and encourage her to dance with another man.
  • Have an on-line ICQ relationship or visit a chat room.

The best time to talk seriously about this fantasy is while flirting, but not in the throes of passion.  As with most sensitive topics, timing is everything.  :-)   I urge you to take the open and honest approach about your sexual needs.  Explain that your fantasy has developed over time, as you've thought about you're own sexuality.  If you're like nearly every man I've responded to on this topic, the idea of exploring a MFM relationship does not in any way lessen your love for your partner.  She needs to hear this message in particular. 

Most women will jump to conclusions and believe that their partner actually desires a swinging relationship.   They may view a shared-wife experience as a means to that end.  It will be necessary to reassure her otherwise, perhaps frequently.

Don't discuss the details about how and when - that's for later.  First share the reasons you want it to happen (see part 1).  Explore how you think you will feel afterwards.  I would suggest a "go slow" approach.  This is your chance to grow and explore your sexuality together over time and strengthen your relationship.  If done right, it will be a wonderful experience and you'll remain happy, sexually fulfilled and very much in love.

• Ex boyfriends that live in your area
• Co-workers
• A guy you meet at a gym
• A friend that lives in your area

The best choice is an acquaintance who lives some distance away and visits only occasionally or someone that you get to know just for the purpose of MFM encounters.  These other options can be trouble for a variety of reasons.

Ex-boyfriends:   She knows the guy and she's already had sex with him, so what could be wrong?  Plenty.  Women have a natural tendency to become attached to whoever they are having sex with.  If he was more than a one night stand, she was at one time emotionally involved.  Sex with him will bring back those emotional feelings for both her and the boyfriend.  This is uncool, so why risk it?

Men, just like women, become emotionally attached to a sex partner under the right conditions.  From time to time,  her new partner will try to convince her to resume a permanent relationship, even when there's no chance she would consider it.  It ruins the event for everyone. 

Friends that live in your area:  I don't discourage this in all cases, but it would not be my first choice.  If they are occasional visitors to your area (or if you visit them), that's more acceptable but proceed with caution.  After she has sex with him, the friendship can change and can actually dissolve and become awkward.  I made this mistake and regret it.  Good friends are hard to come by.  It is better to meet someone for the expressed purpose to have sex than it is to risk a old friendship.  Friends also know where you live, work, play and may talk with other friends of yours.  It is OK to become friends with her new partner to some degree, but don't expect it to have the dynamics of a typical friendship.

A guy she knows from the gym or work:  It is easier for her, because she has already sized him up and he's considered acceptable.  The down side it that he probably knows where he can find her.  Also, he's local.  Local people know others in your area and then you risk the possibility that your shared wife experiences are commonly known.

Propositioning a friend:  Imagine you're planning to ask a friend to participate in a three-way.  How do you know he will agree? If he says no, everyone will feel very stupid and the friendship will likely suffer.  Maybe he will not agree to have sex with the husband present because it is just too embarrassing (there are lots of guys like this).  Again, it will create problems.  Maybe he is impotent.  Get the picture?  My advice is that you should be prepared for most any reaction if you're planning to ask a pal for three-way sex.

Propositioning someone you just met:  What if you are planning to ask someone you just met, say at a nightclub or while on vacation?  She has danced and flirted with this young hunk for two hours.  Perhaps they have kissed and both of them are very horny.  Then she propositions him for a three-way.   The guy suddenly is quite unhappy.  He is not interested in a threesome, especially with another guy present!  He wants her to himself.  Sadly, this does happen.

Your alternative is to proposition through an advertisement.  This way, everyone knows up front the nature of the relationship.

Before you do, I urge you to take sensible precautions.  Don't give out a phone number, address, place of work, identifiable picture or any other personal information.  Do include your area code otherwise expect more mail than you can handle.  Be prepared for an onslaught of email (20-50 messages per day at least).  I suggest an ad that looks similar to the following:

Example Ad

This ad does not reveal much about you and clearly spells out what you're seeking.  You don't want to look through 500 ads so there is a deadline for applying.  When you receive ads, I would immediately delete any that don't have a picture attached.  Also delete any that appear too direct, poorly written or too brief. 

When you find one you like, I suggest you respond with a picture of her that does not reveal her identity and ask for additional information.  Let him know that unless you send him e-mail, he is not to send you any. 

This can be a fun experience for a couple going through the candidates together.  When you think you've found the right man, and you believe he is for real, I might suggest you participate in a suggestive cyber-chat or cyber-sex relationship for a while.  Get to know him, his likes and dislikes and share similar information with him.  This acclimation time make's it much easier for both of you if you decide to meet.

Most men desire to have a 10 inch penis as thick as your arm.  But, if you ever have an honest conversation with a well hung guy, you might find he's not perfectly happy about it.  Why?  Because he's too long for full penetration with many partners.  Vagina size varies significantly and while some are very deep, others are not.  Some women experience pain, not unlike a cramp if a penis or dildo makes forceful contact with the back of the vagina near the cervical entrance.  If the man cannot grind his pelvic bone against her clitoris, it may be very difficult for her to really enjoy the sex and have orgasms. 

Contrary to what you might read, the vagina does not readily stretch in length like a uterus does to accommodate pregnancy.  It can adjust to accommodate greater thickness, not length.  Thick is generally good.  Erotic stories indicate that a women accustomed to the small penis of her husband will over the course of a few minutes be able to accept another man's tool that's several inches longer.  In my experience, this does not appear to be true.  I'm 6.5 inches and have encountered several women that would prefer that I was a half inch shorter because I would occasionally "bottom out" in certain positions.  They never seemed to adjust.  I've also had girlfriends that could accept a 9" dildo so vaginal depth varies.

Here's something else to think about.  A few years back, I encouraged my then girlfriend to have a sexual experience with another man.  We found a guy.  She blew him in his car about two weeks before she actually had sexual intercourse with him and found that he had a 4.5 in penis - one of the smallest she had ever seen.  I was disappointed, hoping for at least six.  A couple of weeks later, she had one of the most intense sexual experiences with this guy that left her breathless.  She had so many orgasms, she lost count and her pussy was sore for a day afterwards.  It is like the old saying, "It is not the wand, it is the magician." 

Another common complaint I hear from women is that well hung guy's don't try to please them in bed.  They assume their size means they don't have to work too hard and it is over too soon. 

If you want a guy who'll please a woman, look for:

• A lover that can stay hard after orgasm or recovers quickly.  Some men can.
• A guy who makes her hot before they jump in bed.
• A stud that can have several orgasms over a two hour period.
• A partner that can delay his orgasm while she cums multiple times.
• A man who will ravish her and make her feel intensely desirable.

So in the end, does size matter?  Most women have a minimum size criteria and this should be indicated in an ad.  To most women, a man is a package not just a penis.  His build, appearance, genitals and intensity in bed all combine together to make him desirable.   To this I say look for character first, not quantity.

Why is this so important?  Even with people you think you know, when you start having a sexual relationship with them, they may feel entitled to intrude into your life in a variety of ways.  He may call one or both of you when it is not wanted.  He may show up at your doorstep, at work or at the gym when you simply don't want him around.  He might talk to others that know you. 

Send him email and arrange to meet him in a public place where you can talk.  Tell him this will only last an hour and you have an engagement later (you can always decide to break the engagement if you want to chat longer).  Explain up front that this meeting will not include sex.  I would suggest a place that serves alcohol and has some privacy (e.g. background music or a sparsely occupied seating area).  Get there early and have a drink if you're nervous.   Have him set where there is plenty of eye contact between her and the prospective new partner.  Let nature take it is course.  If there's chemistry great.  If there's not, don't be discouraged and plan to start over.

If the meeting is going well, there should be flirtation and some level of sexual tension in the air.  If it looks promising, it is a good idea to let the woman and her perspective partner have a few minutes alone to talk.  Make an excuse to get drinks, go to the bathroom, etc.  Later, the couple should ask for a few minutes alone to chat before extending a future invitation for more that just conversation.  If you're both in agreement that this guy will be right for you, then it is time to make future arrangements and set some ground rules.

I would suggest you arrange for a hotel meeting several days later.  This gives you both time to back out if you desire.  Tell him you will send e-mail if there is a problem with this arranged date at least a day in advance of your next meeting.  It is appropriate that you ask the man to pay for a room or at least share the cost (If I were the lucky guy, I would volunteer to arrange for the room) at a nice hotel.  I would suggest a time not too late in the day as you may want to start the evening with a meal, dinner, dancing or whatever will help make this a night she will never forget.

Most ground rules should have been previously discussed via e-mail earlier including the topic of aids testing. 

If you're still ready to proceed, I suggest you stop having sex at least a few days before the first meeting.  Why?  It is one thing to talk about having sex with a stranger and entirely another to actually go through with it.  Yes, this will be very difficult, because sex will be on your minds every minute until the next meeting.  :-)  Being very aroused beforehand will almost certainly make it easier for her.  The sex will be hotter and the orgasm's more plentiful, believe me.  If you can't hold out a week, at least try for a couple of days and don't have sex just prior to the encounter.

Will this be a threesome or will the husband/boyfriend just watch?  Will the both of you start out and have him join in?  Is French kissing appropriate?  Do the men alternate time with the woman?  Will you take pictures or video the events?  Can she have unprotected sex with both of you?  (not recommended).  Will she go to the room with her new partner and be joined by her husband/boyfriend later?  (not recommended the first time).  How long will the sex last?  Is anal sex allowed?  How about double penetration?   It is not important what you decide,  just that you have a discussion about it. 

First time sex in a three-way is usually awkward at first.  This can me minimized if you take things slowly and get to know one another with e-mail.  Get comfortable as a threesome before removing your cloths with conversation.  Chat over a beer.  Flirt with email.  Slow dance.  Tease one another.  This will pay off in the end.

The relationship between the two men will probably be the most awkward.  The husband/boyfriend should find a way to indicate with his woman's new partner when it is OK to proceed and when it is not.  Having a friendly one-on-one conversation is recommended.  Email communications work well for this.

Assuming you develop a relationship over time with her new partner and you both trust him, I would suggest the husband/boyfriend leave the room for 20 minutes.  She and her new sex partner may be reluctant to show their wild side for different reasons.  He may feel uncomfortable with the other man in the room.  She may feel guilty exhibiting too much pleasure.  While alone, they may reach a new level of passion.  When you return, they may be more willing to continue in this manner.

Another twist it to stop after a period of time and ask the new lover to leave for a period of say an hour.  Then have him phone the room and come back later.  It gives you both some time to talk and be passionate in private.  When he returns, she can resume with him where she left off knowing her husband/boyfriend is both excited and supportive.

When you make final hotel arrangements with the new partner, tell him it will end within 2 hours of the time you get to the room.  You can always change your mind and continue for as long as you're both comfortable with it.

The couple should have a non-verbal queue, that they can use in the hotel room indicating they want a time out or the whole thing to end.

Keep the sexual encounter to just that.  A few hours of sexual activity is enough.  For most couples, once or twice a year of this activity is plenty.  You don't want a steady diet of sex outside of the relationship.  If you want a repeat performance, take pictures or video the event and re-live the experience at home.

Make it a threesome.  The presence of a husband/boyfriend will help her keep emotions in check.  Realize it will feel awkward for her and her new lover.  It will take an adjustment period where the three of you get used to each other in the bedroom, but it is nothing you can't work through.  If you take it slow, this is not difficult.  Have a drink, start with a massage.  Move to heavy petting and let things happen naturally.  ;-)

It is best not to "go on a date" alone - especially at first.  It also reduces the anxiety for the husband/boyfriend.  I let my girlfriend "date" and stayed home wondering what was happening.  On one level, this is exciting, but on another it makes for very anxious moments and mixed feelings.  If she arrives home an hour late, it will feel like minutes for her and days for him.  When she comes home, the man is more than ready to have sex but she will have had time to cool off.  She and may not want sex at all.  Talk about disappointment.  :-(   The sex immediately after (seconds later) she's been with her lover is the very best of all.  Don't miss out by staying home.

This is not the place for romance.  If an evening out for her is agreed upon, it should NOT include a dinner, dancing, lot's of discussion and subsequent sex.  This is "dating" mode.  It is the way in which we court a member of the opposite sex and establish a potential lifelong partnership - but inappropriate for a shared wive/girlfriend.  If a date is arranged, it should be short (i.e. for a drink, then upstairs to the hotel room).  At a predetermined time, the husband/boyfriend should knock on the door. This can be a few minutes after her lover departs or he can still be there.  The couple can decide.  Another way to arrange this is to have all three of you there in the hotel room when you begin, then the husband/boyfriend can leave for a while (e.g. 30-45 minutes) and return.  Again, this is not suggested the first time.

There should not be any discrete communications between the woman and her new sex partner.  No daily e-mail banter, phone calls, mail, flowers or personal visits.  It is my suggestion that the man maintains the dialog with the new partner in e-mail format only and he should not be allow to talk your wife/girlfriend directly.  This is not meant to control your spouse/girlfriend, it is to keep this new partners desire for more of a relationship firmly in check.  His communication will be less romantic if he knows the boyfriend/husband is reading the mail.  As stated earlier, I have a rule: 

When I contact you, you can respond with mail.  If you don't hear from me, then we don't want to hear from you.  If you break this rule, it is over.

Talk about the emotions she feels afterward.  It is OK if she likes him, but if she feels something more, you both should be careful about future meetings.  Feelings of guilt sometimes set in at first, but with reassurance from the husband/boyfriend, this will pass.  Have a heart-to-heart talk about how both of you feel several days later.  It is a new experience for both of you and the relationship you already have is always the first priority.

Keep the romance alive within your own relationship.  Don't make the grass look greener somewhere else.  Treat her like a princess at the center of your world.