Here is an idea, don't take your wife for stupid. Really don't take your wife for stupid when she cooks, cleans, raises the kids, has a master's and is halfway through a doctoral program and has caught you in lies before. Don't assume that she won't find things out, that other people won't tell her or that you are suddenly so bright that you can pull one over on her.
Don't lie and say you aren't talking to someone when you are. Don't tell her that you are "just friends" and then treat said person better than you treat your wife. Don't say that you never discuss your wife and then bitch about your relationship or your wife. When your wife says a relationship you have with another woman is too close, take it as a hint that it IS TOO CLOSE. If you have to lie, sneak around, hide things, etc....guess what, the relationship is more than friendship and inappropriate.
if you are sending this woman things in the mail without telling your wife, there is something wrong, and when you have done this before and lied to wife for a year, anticipate that she will be blowing her top sometime soon. Also note that that same stupid wife you thought you could trick will ensure that one of two things happen, either this woman and you quit all contact, or you and wife will quit all contact. Think about it.