[dijichi2]

Ignore your external DNS issues, you need to get internal DNS working, that is the key.

'dig mail.jzeller.com' is the correct command to run. you need to get a correct response to this question before you can proceed, it should return an A record with the IP address 192.168.1.110. Put the record in your internal DNS - in your jzeller.com zone should be something like 'mail IN A 192.168.1.110', if you're using BIND.

from your dig responses, you seem to be confused about split-DNS. split-horizon (split-brain in M$ parlance) DNS means that on your internal network, you 'fake' responses for domains you are authoritative for with internal addresses. currently, you have set your internal DNS server to respond with external addresses, which defeats the point of having the internal DNS server, and you have a single @ A record.

change the internal jzeller.com zone to have the following:

mail IN A 192.168.1.110
IN MX 10 mail.jzeller.com.

this should be all you need.

'dig mail.jzeller.com' should return 192.168.1.110
'dig mx jzeller.com' should return 10 mail.jzeller.com.