SMTP

A good guide is probably better served at docker-mailserver introduction.

Useful services:

• https://aboutmy.email/
• https://mxtoolbox.com/SuperTool.aspx
• https://multirbl.valli.org/lookup/
• https://www.reddit.com/r/emaildeliverability/comments/1ssgki5/not_all_email_blocklists_are_worth_worrying_about/