This question was originally on SO but it was closed since it is considered off topic.
I am interested to build a mail service that allows you to incorporate custom logic in the your mail server.
For example, user A can reply to
[email protected] once and subsequent emails from user A to
[email protected] will not go through until certain actions are taken.
I am looking for something simple and customizable, preferably open-sourced. I am fluent in most modern languages.
What email servers do you guys recommend for this?
Mailgun looks promising, but are there any simpler options?