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.
and I'd like to say, I'm pretty darn good at running mail servers after 30 years of doing it.
@jerry It should be sufficient to put the required contact information into the instance info box on the front page before asking to be unblocked, but I fully understand if you don't want to.
@galaxis I am going to look at doing that.
@jerry @galaxis Alexander is right, their policy is that they need contact information on the webpage of the domain. I (running Mailservers for only 20+ years..) had similar problems after migrating my MX to a different provider. I setup a webpage for them with the info they demanded, they whitelisted my MX, I removed the info..😏
@beirer @jerry @galaxis Yeah, we have to email tosa@ every time customers who host their own mail servers move to different IP space. It’s completely ridiculous. Even when you are a Telekom customer and have IP space from them. They are however really responsive. They helped me over the Easter weekend once. So they make the best out of a really stupid practice IMHO.
Jerry 🦙💝🦙
Alexander Bochmann
beirer
Florian