Root cause of the issues: Trying to connect to an SMTP service to send OTP's that began to block me after "suspicious activity".

Just switched to an actual transactional email service so it might actually work for a bit. (oops, still need to get verified to send more than 100...)

I own https://mailpace.com - if you sign up and set up your DKIM records you can send right away. Drop a note to support@mailpace.com once you're up and we'll remove your rate limits.

Thank you for the offer on the short notice! I ended up getting verified with the other service and am happy to enter have a little stability now. I will check out mailpace though!