I have used T-bird just as it is set up for years. And this AM it won't send. This is the message I get. An error occurred while sending mail. The mail server responded: 4.1.8 invalid/host-not-in-DNS return address not allowed. Please verify that your email address is correct in your Mail preferences and try again. I use one server as my incoming server and verizon is my outgoing server. I did add the junk email filter lately and noticed in the last few days that it has been asking me if I want to compact my folders every time I delete a message. And it usually asked me only once a month. I wonder if these problems are related. But, long and short, I am not able to send email addresses and nothing has been changed since yesterday when it was working.