Some very good points were made here.  I do believe you can become close online with a member of the opposite sex and it can lead to more than just friendship - afterall it happens all of the time.  Please be careful about sharing emotional situations and issues - especially via private messages because as you share with each other and sympathize with each other, you will become closer and an attraction beyond friendship could develop. 

Finally - I would be suspect of your husband being so willing to allow you to enter into a relationship like this.  Trust is one thing but he, in my opinion, is throwing you into temptation.  The question I would have is why.

What a strange illusion it is to suppose that beauty is goodness.
~Tolstoy~