I have started receiving multiple copies of emails. Looking through my logs, the reason that I am getting multiple copies is that the remote servers are retrying messages because they are not getting the 250 Queued As message back. (I know this because I've ssh'd into my Linode and have done the SMTP conversation by hand, using telnet.)

My mail server is in my office, on the end of an ADSL connection. If I talk to the SMTPd from my LAN, all goes as expected. If I do it remotely (like from my Linode, which is also the backup MX), I either never get the 250 after sending the <CR><LF>.<CR><LF>, or sometimes get a delay in response to RCPT TO:, or DATA.

From my Linode, if I use Lynx to go to the same server, where I run my intranet/extranet, I get no problems talking HTTP.

Anyone got any idea what might be amiss? The multiple messages are annoying, but when people start getting notifications that their messages couldn't be delivered after I have received them many times - well, that's when it will get worse.

Does your office mail server have DNS issues? Can it do forward and reverse lookups of internet IP addresses OK? Is it behind a firewall? Some (eg PIX) can break SMTP transactions.

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Rgds
Stephen
(Linux user since kernel version 0.11)

Thanks for your reply.

It is behind a firewall which does NAT and passes on SMTP, etc., packets by port-forwarding. The firewall is part of the D-Link ADSL router. Never given problems before.

DNS problems? I don't know. Sometime late yesterday the problem resolved - but not as a result of all the fiddling that I had been doing, it just happened. When I saw that I wasn't getting repeating mails anymore, I SSH'd into both of my Linodes, tried the telnet test again and got the acknowledgments back without any problems.

Mail was going _out_ OK, so it must have been resolving then, and I was able to use other services normally. However, I cannot eliminate some transient DNS issue.

I almost wish that it had stayed broken as the sudden disappearance of the problem makes it all the more puzzling.