[Exim] retry timeout exceeded

Hello,

I have set up exim as my local SMTP server for a very low number of
users and to run mailman with it. The machine it is installed on is
Debian Potato box with an ADSL connection to the outside world.
Mailscanner is installed and so is mailman, which is running two mailing
lists with low traffic.

Strangely enough sometimes my mail gets bounced with various error
messages, but all of them end with the following statement: retry
timeout exceeded.

That statement can be preceded by errors like:

remote host address is the local host
forced defer: All deliveries are deferred

The last one is the most common.

The stuff regarding this type of error I could find on the web was
mostly related to systems on dial-up, which this one isn't. Does anyone
have a clue what is happening?

Regards,

Walter

--
You have a morbid aversion to dying. You probably resent the fact that
you're at war and might get your head blown off any second. - Col.
Sanderson in Catch-22