My Mac Mail 3.5 can retrieve the mail from my comcast account. It can't send mail I get a message stating The sender was rejected by the server smtp.comcast.net. I have changed my port settings from 110 to 587 and 25 and 4something as suggested by the comcast technician. Nothing works. I've never had this problem before. I have a G5 and OS 10.5.5: This is making me crazy!!!!!