Missing the trailing dot in zone file
Missing the trailing dot in config authoritative name servers is a common mistake committed by network administrators. I admit that I always forget this important aspect. As a reminder, I now jot down some easy reference to alert myself aware of this carelessness.
Forward lookup of mx for zome example.com
; zone example.com.
@ IN MX 10 mailhost.example.com
[ the final part should be mailhost.example.com.]
@ IN MX 10 mailhost.example.com.example.com.
Reverse lookup of 192.0.2.1 to produce host.example.com
; zone 2.0.192.in-addr.arpa.
1 IN PTR host.example.com
[ the final part should be host.example.com.]
1 IN PTR host.example.com.2.0.192.in-addr.arpa.
Keep the above in mind as much and as long as possible.