K.P.
We are raising two children who were not born to us and have seen this over and over with both of them. We limited phone contact and have not had any personal visitation. We have made no limits on contact through the US Postal mail, but do not allow any emailing.
While their mother is supportive and understands she can't raise them, it doesn't change the emotional impact contact has on the kids. As much as they like to pretend they are handling everything, the fact of the matter is, they have a lot of mixed emotions and don't know what to do with them.
We do a lot of talking about emotions around here. I continually remind them it is okay to be angry, sad, relieved etc. I accept (although admittedly don't like it) when those emotions are directed at me or my husband. Along with allowing them room for their feelings, though, we continue to hold them accountable for their behavior.
The most important lesson I have learned through all of this is that, as parents, we can't always "love enough", but we can be vehicles to help introduce our children to a God who can.