mail2.sezampro.rs has no MX records.
Question and response
Question
dig mail2.sezampro.rs. MX
Answer
The response has no answer records.
Authority
sezampro.rs. 3600 SOA c-olymp.sezampro.rs. hostmaster.sezampro.rs. 2017062014 900 600 86400 3600
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0