web1.bitrix24.com has no MX records.
Question and response
Question
dig web1.bitrix24.com. MX
Answer
The response has no answer records.
Authority
bitrix24.com. 900 SOA ns.bitrixsoft.com. hostmaster.bitrixsoft.com. 2013102201 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0