http://feeds.feedburner.com/~r/PsychologyBlog/~3/104099412/communicating-persuasively-email-or.php - Communicating Persuasively: Email or Face-to-Face?
So, if you want to persuade someone with whom you have a competitive relationship - whatever your and their gender - email might be a better choice. On the other hand, if your persuasion attempt is aimed at someone with whom you have a more cooperative relationship, face-to-face could be a better choice. Unfortunately, it isn't always possible to see someone face-to-face, so it's very useful to be aware of the processes operating in both face-to-face and online interactions.
Interesting to think about your communication choices in this way. I am not sure how the phone and IM fit into things.