[enh] user blacklist applied before global ip/email filters

I think that rejecting with a permanent 5xx error in case of user configured blacklist should happen BEFORE the global rejecting rules because they would generate a defer 4xx error instead, so to be repeated many many times until the message will be bounced by sending server.

This would save server's resources and many log records! :)

Trace the SMTP message-processing path where user-configured blacklists and global IP/email rejecting rules are evaluated. Confirm the current defer-versus-permanent rejection behavior, then verify that a matched user blacklist is handled first and repeated delivery attempts are avoided.

Written by the indexing model from the issue text.