mail.acelerate.com has no MX records.
Question and response
Question
dig mail.acelerate.com. MX
Answer
The response has no answer records.
Authority
acelerate.com. 3600 SOA ns1.acelerate.com. dnsadmin.acelerate.com. 2025060400 7200 3600 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0