I received an email this morning with instructions about migrating to a new webmail service. The URL on this message traces to a server overseas. Is this a valid email???
Likely not valid, but would need the headers to trace it and report it.
That's an email address, not the headers in the email which give details of the specific route the email took.
That said, it's extremely doubtful there would be such a thing from a German t-online.de domain. I'd automatically treat it as a phishing attempt to gain your login information.