How to disable mail receiving by local users without deleting their accounts
On my server, sendmail is configured to receive mail for all local users.
And that includes "system" users, like root, backup, and mail.
So how can one forbid them to receive email, without deleting their accounts?
That's actually quite easy.
First, enable relevant sendmail feature: open the file /etc/mail/sendmail.mc
and add this line somewhere in it:
FEATURE(`blacklist_recipients')
After that, rebuild the actual sendmail config and restart sendmail:
cd /etc/mail; make; service sendmail restart
Second, edit /etc/mail/access file and add REJECT rules for them, like this:
backup@shpakovsky.ru REJECT
After that, rebuild the actual database:
makemap hash /etc/mail/access < /etc/mail/access
And last, test it: write an email to forbidden e-mail address and enjoy automated response from MAILER-DEMON :-)
More information regarding anti-spam protection you can find in the official sendmail documentation (archived version).