He married her in order to forget his ex-fiancée; and the ruling on correspondence between the sexes
Question

                My husband came home from work and told me he did not want to be married any more because he wants to be alone and than we went to Jumah. That Tue. After having intercourse he told me his ex fiancé found him by e-mail, a week prior. He allowed me to see the e-mail she sent him. To my surprise there was more than 1. They were e-mailing each other but he did not tell me that. In the e-mails they were discussing each other’s body parts. He was calling her everyday that he had to work & said he will not loose her again. He said he married me for two reasons. He didn’t want anyone else to have me & thinking it would get her out of his system but it did not and he has been looking for her since and now they have found each other. He has giving the girl our mailing address as well and she has used it. I spoke with her asking if she would not bother with him. She told me he is a free man. I know he is allowed up to 4 wives. He has his name on a list with the high school graduated from so that other people can get in touch with him. So far 3 females has found him. I would like to know if it is okay for my husband to have female friends and they are all non-Muslims. Please help me. Sometimes I feel he doesn’t want me for the right reasons. We are overseas and she is in the states & now he wants to go back.
Praise be to Allah.Allaah has made marriage one of His signs, 
    and has created love and compassion between the spouses, and He has made each spouse a garment for the other. The basic principle regarding 
    marriage is that it should be lasting: it is not permissible for either spouse to go against the purpose of marriage. Your husband should have 
    feared Allaah and had a good intention before embarking on marriage. So long as he married you with your consent and all the conditions of 
    marriage were fulfilled, then your marriage is valid and there is no doubt about it. 
It is also haraam for him to establish 
    relationships with women who are “strangers” to him [i.e., non-mahrams] and to correspond with them, so how about if that correspondence also 
    involves obscene words such as words of love and romance? See the answer to question no,
    23349. 
With regard to yourself, why don’t you speak 
    frankly with your husband and advise him? That may bring him back to his senses. Or you could ask some good people to intervene and advise him. 
If he cannot forget her, then it is 
    permissible for him, according to Islam, to marry her if she is a kitaabi [one of the People of the Book, i.e., a Jew or a Christian], subject to 
    the condition that he repents from having had haraam relationships and he comes back to being chaste. 
In that way he will protect himself from 
    falling into haraam actions. Allaah permits Muslim men to marry chaste women from among the People of the Book (Jews and Christians). 
You have to be patient and not hasten to 
    separate from him. Perhaps if you stay with him and are patient with him, and keep on advising him, that may be the cause of his being guided and 
    coming back to his senses.  
If he insists on separating and continuing to 
    do haraam things, then you should not feel bad about it and should not be keen to stay with him. Whatever the case, we ask Allaah to guide us and 
    you and him and give us strength. 
And Allaah knows best.