How I fixed "Host not found, try again" for incomming email ?

your server is asking the MX in charge of my-domain.com.bd which return mail.my-domain.com.bd and search for its IP and do not find it.

Regards,

yes, i think i am understanding the problem, i was trying mxtool box i see it connecting to the IP of my my-domain.com.bd , which is odd . i am looking at my zone record now, but tell me please , when i ping mail.my-domain.com.bd : it returns the right IP which the ( i checked ping from other server)

if mail.my-domain.com.bd returns the right IP, then what is the issues?( oviously, i am doing wrong but not understanding from DNS point of what that could be)