We run a small courier mail server (courier-esmtpd). It is configured to accept mail from authenticated clients without recipient restrictions and mail from everywhere to local addresses:
Now we get some spam mails where the from-address is set to something like
info(at)mydomain.tld and another local mail address as recipient.
I'd like to block those mails. Yes, most of the time SpamAssassin marks them as spam but I think the better way would be to directly reject mails with spoofed sender addresses.
Is it possible to configure courier-esmtpd to block mails sent by an unauthenticated client from an external IP address and a local from-address?
It is important that authenticated (legitimate) users are able to send mail using any from-address like
user(at)mydomain.tld even from an external IP address (PC at home, etc.).
Edit: I tried to set the configuration option
badfrom (at)mydomain.tld in file
/etc/courier/bofh, but then all mails with corresponding return addresses are blocked, authenticated user or not...