spam
- https://www.mail-tester.com/
- https://glockapps.com/
- DMARC
- grscripts.com – ASSP based plugin for cpanel to stop spam.
- https://mxtoolbox.com/blacklists.aspx – check if IP black listed.
- https://rspamd.com – Bayesian based spam filter. Similar to Spamassassin
Incoming & Outgoing spam filer (SAS)
- https://spamexperts.com/ – cost like $1 per domain for service providers.
- https://www.mailchannels.com – used by hosting providers to stop outgoing spam.
- https://www.mail.baby – only out bound spam filtering. $1 per domain + 20 cents per 1000 emails.