Spam Resource
Verifying email addresses through methods akin to what we now think of as confirmed opt-in (COI) or (DOI) isn’t a new thing. Mailing list software Majordomo added support for verifying new signups way back in 1996. I don’t remember exactly when it became common to validate that opt-in via an email click, but I remember building email click tracking — sending out a unique indicator per subscriber and taking action or updating a status — for my own purposes way back in late 1997 as part of a spam filtering system I had built at the time. Then in 1998 I started a COI/DOI email list for my friend’s jazz club using custom code (not captured by the Internet Archive until 2001). So, it’s been done before.
Are you looking for an open source sending MTA solution?For big senders, commercial MTA platforms like PowerMTA or MailerQ are usually the way to go. But for those of you looking for an alternative, ZoneMTA might be something for you to check out.