I hope this is the correct forum for this question.

I'm setting email up a new Netbook.
I have the POP side of the accounts working fine but am not sure of the way SMTP works.

The desktop computer at home is on Compass and uses a Compass SMTP server.

The netbook will be on Compass when on the wireless network at home but while away from home could be on either a free WiFi hot spot OR on Vodafone 3G.

What should I do about specifying an SMTP server in these circumstances?
Do you have to set up one for each and switch to the appropriate one at the time?
(and, if so, what SMTP server can you use when on WiFi?)
Can you set up one SMTP server that you can use in all circumstances?
Thanks