Reject undesired email during SMTP.
This feature has already been requested in pieces in multiple places.,,,. I am just combining these requests into one.
Undesired email should be rejected during the SMTP dialog.
Why: If email is rejected during SMTP, no bounce message ever needs to be sent. This decreases backscatter, i.e., bounced email sent to somebody other than the sender, thus a type of spam.
Currently, disk quotas and mailbox sizes are not checked until after incoming mail is accepted via SMTP. Likewise, spam detected by SpamAssassin is not blocked until after it's accepted via SMTP.
The DirectAdmin developers would most likely have to add code other than Exim to achieve this. Strategies have been previously discussed.
Mailbox size and disk quota should be tested, and mail analyzed by SpamAssassin, after its body is accepted, but before a final 200 OK is sent to the SMTP client.
See the about section in files.directadmin.com/services/easy_spam_fighter/ (also mentioned in docs.directadmin.com/other-hosting-services/preventing-spam/general#spamblocker-install-and-extra-modules)
I saw Easy Spam Fighter mentioned in a custombuild recipe, and I did install it. However, the documentation is fragmented, in many places, and some of it is dated as far back as 2015 or so. It was hard to tell just what it's doing. Is it really blocking during SMTP? If so, thank-you, I stand corrected. (Still need to handle mailbox size and disk quota.)
I think there is a lot of knowledge in many places, forum, old knowledgebase, new documentation, plus file downloads, and it's hard for me to collect it all into my brain and put it all together.