fetchmail/sendmail: Domain of sender address does not exist

[Anton Shterenlikht]

I'm running sendmail, and using fetchmail to fetch
my mail from the university IMAP server.

I sometimes see fetchmail complain:

fetchmail: SMTP error: 553 5.1.8 <admin at system.mail>... Domain of sender address admin at system.mail does not exist

And this is doubled in /var/log/maillog:

sm-mta[14642]: r270BO3L014642: ruleset=check_mail, arg1=<admin at system.mail>, relay=localhost [127.0.
0.1], reject=553 5.1.8 <admin at system.mail>... Domain of sender address admin at system.mail does not exist

How do I set fetchmail and sendmail to fetch
such emails?

Thanks

Anton