Re: [exim] Re: undelivered messages

Gasperi Michael said:
> Hi,
>
> I found out that there's a reject if the virus scanner tries to send
> back (smtp-backdoor) mail to exim and our internet connection is broken,
> this only happens (of course) only for our internal mails.
>
> The following message appears in reject.log
>
> SMTP protocol violation: synchronization error (input sent without
> waiting for greeting): rejected connection from H=[127.0.0.1]
>
> it behaves like it were a permanent error (5XX) ...

Your virus scanner is misbehaving - not following proper protocol, sending
commands before Exim has sent its greeting. I expect Exim is trying to do
a reverse DNS lookup on the client IP, which is timing out when your
internet connection is down. This means there's a long delay before the
greeting is sent, and your virus software doesn't want to wait.

Several possible actions come to mind:

1. Fix your DNS resolution so it can resolve local IPs to hostnames
without needing the internet connection.

2. Tell Exim not to do reverse resolution on internal networks

3. Get your virus scanner software to obey SMTP better

4. Tell Exim to relax its protocol checking for internal hosts.

The Exim documentation will help you with 2 and 4.

Peter