smtp.SNDSY.RU has no MX records.
Question and response
Question
dig smtp.SNDSY.RU. MX
Answer
The response has no answer records.
Authority
SNDSY.RU. 3600 SOA ns.iprojects.RU. noc.iprojects.RU. 2023051298 10800 1100 864000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0