http://y5wnzw4e6i7srm2gqadlow5anhlaj5avdkzbwzbmrxwkygxdp7ffieqd.onion/blog/firehol-considered-useful.html
Before I dump my firehol config, let me say I am intending to accomplish here: Submission/IMAP/POP3 port is intended for TRUSTED users to use so that your system can send mail out, which means it would be ok to set this to a whitelist of some kind. As Submission is being used to accept mail from clients, (in my opinion) the SMTP port should NOT allow AUTH command to be used.