mail3.onemainfinancial.com has no MX records.
Question and response
Question
dig mail3.onemainfinancial.com. MX
Answer
The response has no answer records.
Authority
onemainfinancial.com. 3600 SOA NS87.WORLDNIC.com. namehost.WORLDNIC.com. 126022412 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0