mx-3.pobox.com has no TXT records.
Question and response
Question
dig mx-3.pobox.com. TXT
Answer
The response has no answer records.
Authority
pobox.com. 3600 SOA fmns1.messagingengine.com. postmaster.messagingengine.com. 2026021600 86277 600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0