Exim debug message receive

To debug message receive process in Exim, run:

# exim -bh SENDER_IP

Example:

# printf "EHLO aaa\nMAIL FROM: aaaa@example.com\nRCPT TO: john.doe@abc.def.com\n" | exim -bh 12.34.56.78 2>&1 | less

It will show evaluation of all ACL rules and other checks. Other useful Exim tips: http://bradthemad.org/tech/notes/exim_cheatsheet.php