rcp.o2.cz has no MX records.
Question and response
Question
dig rcp.o2.cz. MX
Answer
The response has no answer records.
Authority
rcp.o2.cz. 300 SOA dns.iol.cz. hostmaster.iol.cz. 2022012956 900 3600 648000 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0