Reject mail from invalid domains

[Michael Kain]

Jorge Costinha wrote:
> hi all,
>
>      im using Fedora core 6, with Mailscanner 4.59.4 and sendmail 
> 8.13.8. I want to block email from invalid domains. Can i do this with 
> Mailscanner/spamassassin or has to be done at MTA level?
>
> thanks.
If you mean unresolvable (by your dns) domains, you would do this:

edit /etc/sendmail.mc and look for this line:
FEATURE(`accept_unresolvable_domains')dnl

add dnl to the beginning like this:
dnl FEATURE(`accept_unresolvable_domains')dnl

save file.

# m4 sendmail.mc > sendmail.cf

restart sendmail.