Postfix and remote sending

[Nathan Aubrey]

I use a postfix server to send email through, but using a laptop, I'm often 
connected at other locations. Without having to continually add my remote IP 
to the my_networks section in postfix, is there another way to send email 
through my mail server?

I have for the time being setup a gmail account which allows for sending mail, 
but some of the mailing lists see the Return-Path is different from my email 
address because google changes it, so it is not always usable.

What suggestions would you make or what do you do in this case?

Nathan