Do I need MX record at all?

[unix at edify.com]

>>You need an MX record to tell the outside world that they should send 
>>mail for your domain to the Checkpoint firewall.  You probably don't 
>>need other MX records to relay from Checkpoint to sendmail and then to 
>>Exchange.
>>Barry Margolin, barmar at alum.mit.edu
>>Arlington, MA
: Ok, Thx. I have only 1 MX record. This weekend, it will be pointing to a
new machine name & a new IP address. I was more worried about the changes
that I am doing with MX records should propagate quickly to the outside
world. Hopefully the TTL of 660 should help. Thx, again.
Ragu