I am a Centurylink Mail user. Like the previous person, they claim it is not their problem even though the message indicates it is their server that rejects the sending mail message. They point their finger back to Mozilla. I did this dance with Time Warner once before I changed to Centurylink. FYI, I got an email from Centurylink indicating they are making changes to their mail software to provide improved service. My problem: I have 5 email accounts working under Thunderbird. Everything has been working fine until last week. FYI, I can receive email with no problem. However, on sending mail, I started getting the error " An error occurred while sending mail. The mail server sent an incorrect greeting 4.3.4 allocated resources exceeded". This was happening on all the messages I tried sending. A day or two later, I was able to get some email out, I thought, but people were not getting them. Or if they got them, it was several days late. Then, during the week, the problem seemed to go away. My email were getting through. This morning, I am having the same problems again. I tried restarting Thunderbird, sent a test message to myself. It worked fine for the first message. On several succeeding tries, it failed with the above message. At the moment, I cannot send to anyone. Talked to Centurylink twice this morning. Not their problem. Use their web client.