[expert] Saving ifconfig settings

[Rob Fleetwood]

Can anyone point me in the right direction as to how to make changes permanent 
in ifconfig?  Example: my default ifconfig reports the MTU setting at 1500.  
Using DSL, this setting will not let me transmit e-mail.  A setting of 1452 
for MTU will.  However, I have to change to 1452 manually.  Where would it be 
saved so that I don't have to manually save it?

Thanks in advance.
Rob