If you have 'conenction reset' or 'connection timeout' while in 'DATA' state, one of possible reasons is an 'MTU discovery' problem when either your or remote server have closed 'ICMP' in firewall.
Everything could be found in maillog if interpreted accordingly. If you can, please do grep for all 'm1BDYj Yo032697' entries in all maillog files.
When I run 'mailq' with no parameters, I get a long list, most with these 2 messages: Deferred: Connection reset reply: read error Given the long list, I wonder if it's a good idea to once in a while flush the queue -- if so, how to do this?
When I run 'mailq -q (using the domain of the messages not received), they all show: reply: read error There are about 6 messages like this dating back about 3 weeks.
Please open your email client and re-send the message from the sent messages folder." Was there something else I should have done while in telnet?
Do I have a problem at my end, or is it an issue with the recipients?
Is this because sending via telnet, am I bypassing my mail server? If manual test went without errors and second 'mailq' shows no more messages then the message was sent (there should be a log entry for that).
If manual test was OK, but mailq still shows 'read error' that means you have network problems.
Looking further at the log, there are a variety of "stat=deferred" messages with various messages like "operation timed out", "greylisting in action", "please try again later", etc.
(I can't tell whether most of these were received or not). First try to send message will always be declined by remote server with some kind of temporary error message. Remote peer 'remembers' your first try and when your server reverts back to this message and sends it again, it's now accepted and all further messages are accepted for some time period. Choose any message that you are sure was send but never was delivered and find all log entries about this mail job.