This is really quite fascinating. There is exactly one ISP that is blocking mail from the mail server I run, which is used to deliver mail for infosec.exchange - t-online.de. It annoys me to no end that I see people try to subscribe to infosec.exchange and the confirmation emails are rejected. So, I contacted their postmaster, and to their credit, they got back to me very quickly, but they are basically saying "yeah, you need to use one of the big mail providers if you want to send mail to t-online subscribers".... Ok then. My apologies to any t-online subscribers (who probably can't see this anyhow), but you'll apparently need to use a different email account to register.
@jerry that sounds like somebody there misunderstood what you are doing. I got my Mailserver whitelisted there, I think somebody misunderstood non commercial/private as dialup running from home with dynamic IP.
They however usually - at least for Germany
- require some sort of imprint on the website of the domain the MX is running on.
@mutax @jerry I think T.O perfectly understands this is a small operator, but their stance is just "use your provider's (ISP, Hosting company) SMTP infrastructure so that we can complain to someone who cares if you send spam".
They completely ignore the fact that as an individual/small business, I'll need to set my SPF up so that any other clients of my ISP can send mail on my behalf. (If the sender cares about SPF but not DKIM).
(cont'd)
Jerry 🦙💝🦙
mutax
chexum