Comment by bb88
15 days ago
I did that too years ago, but the management of it was kind of annoying. DKIM was just getting introduced when I stopped using it. SPF had controversy. I understand both of those are awesome now.
The biggest issue was if your ip address got listed in a RBL (Realtime Blackhole List), and then nobody would talk to you. Some were easy to get off, others were permanent blocks, and I found those to be constantly interfering with the delivery of mail. At least the rejection would usually tell you which RBL blocked you.
Most RBLs are scams. No competent mail admin uses them to block mail ever.
…lots of major mail services do?
https://www.fastmail.help/hc/en-us/articles/360060591413-Spa...
https://senders.yahooinc.com/smtp-error-codes/
https://www.xfinity.com/support/articles/email-errors
Honestly those are used as weights now in some kind of obscure calculation (or maybe not so obscure calculation but I still don't understand it).
What I really learned during that time is that mail servers have well known IP addresses and reputations. And you can say all you want SPF/DKIM fixes that, but the reality is when google sends your email (even with your custom domain) it gets received.