mail2.3uu.de has no MX records.
Question and response
Question
dig mail2.3uu.de. MX
Answer
The response has no answer records.
Authority
3uu.de. 86400 SOA ns1.opst.de. support.variomedia.de. 2025020831 28800 7200 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0