I just told Deutsche Telekom to stuff it when they wanted to compromise my privacy for the privilege of one of my users to send mail to one of their users.

It all started with this message in my log (this is only the important part, no timestamps or email adresses are important in this case, the recipient was at t-online.de):

554 IP=195.16.73.49 - None/bad reputation. Ask your postmaster for help 
or to contact tobr@rx.t-online.de for reset. (NOWL)

Btw. I am the postmaster.

In their policy, they pointed me to this paragraph:

There must be a domain and website with direct contact information
easily deducible from the delivering IP's hostname (FQDN). (see
RFC 1912  FCrDNS, EU Directive 2000/31/EC Article 5)

RFC1912 is something I of course follow, you can’t have a domain without a correct SOA record (which is all that RFC requires). As I am not in the EU (Norway is in EFTA, but as of today not in EU), I didn’t know about that EU directive and actually don’t care either. Besides, after googling, that directive has been overruled in 2022. And it doesn’t apply to private entities, just businesses (“service providers”). I am not a service provider, even though I provide email services to members of my family (which I deem a private matter).

Anyway, they require me to have an immediate method of contact, and no, email is not good enough, and it has to be on a webpage with the same hostname as my email server. Sheesh. The web address of my mailserver is a landing page for my family’s webmail. Again, that is something I deem a private matter.

So, if you are in Germany, and your main email adress is at Deutsche Telekom, and you actually want to communicate with people in the world instead of just other customers of Deutsche Telekom, get a different email address. If you have a business, even more incentive to not use T-Online for email. T-Online/ Deutsche Telekom is unusable for email because of stupid rules like this. Hell, I don’t have a rule like this on my mailserver, nor have Google or even Microsoft. Or even web.de, I hear they give you free webmail there as well. I can tell you that Google is really good at filtering out spam, and if you care about privacy, there are providers like Proton Mail. But whatever you do, give Deutsche Telekom a wide berth when choosing your primary email address.