rs.eserver.net has no MX records.
Question and response
Question
dig rs.eserver.net. MX
Answer
The response has no answer records.
Authority
rs.eserver.net. 1800 SOA ns1.rs.eserver.net. hostmaster.rs.eserver.net. 2025082401 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0