SMTP with mail.example.de

[Praktikant81]

Good evening,

I have a problem with sending SMTP.
My domain is example.de and the SMTP server can be reached via mail.exemple.de.
Unfortunately, mail.example.de will be dissolved internally.
example
Unfortunately, I can no longer change mail.example.
Unfortunately, I haven't found anything that could be the cause or what I would have to change...
What am I doing wrong

[Praktikant81]

So I was able to fix the problem.
In the Docker server's hosts file, there was an entry for mail.example.de that pointed to 127.0.1.1.
It was probably entered when the system was set up.
Now everything works as it should