lib.ntua.gr has no MX records.
Question and response
Question
dig lib.ntua.gr. MX
Answer
The response has no answer records.
Authority
lib.ntua.gr. 86400 SOA achilles.noc.ntua.gr. noc.ntua.gr. 2025052601 43200 3600 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0