It is important to verify that MX records can be seen.  To check use the dig command with the -t option which will allow you to do an MX lookup.  This example shows the MX records for the myexample.com domain which is using the ns.example.org server as the mail server.

dig -t MX myexample.com

; <<>> DiG 9.2.4 <<>> -t MX myexample.com
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4499
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1

;; QUESTION SECTION:
;myexample.com.               IN      MX

;; ANSWER SECTION:
myexample.com.        86400   IN      MX      10 ns.example.org.

;; AUTHORITY SECTION:
myexample.com.        86400   IN      NS      ns.example.org.

;; ADDITIONAL SECTION:
ns.example.org.       86400   IN      A       21.14.226.132

;; Query time: 79 msec
;; SERVER: 21.14.226.132#53(21.14.226.132)
;; WHEN: Sun Dec 17 12:08:39 2006
;; MSG SIZE  rcvd: 95