A lot of ISPs won't let you send e-mail if you aren't on their network. For example, Time Warner Cable won't let you use Roadrunner while outside your home. Oh, and my college e-mail won't let me send mails from my college account if I'm not logged onto their network.
As far as I know, there is no way around it.
That's why I'm now the proud owner of a gmail account ... as it's web-based and they'll let you send from anywhere.
So, my recommendation is to get a web-based email such as gmail (or Yahoo, Hotmail, etc). You can always set up your accounts so it all looks as if it is coming from the same place....
'Bout the only thing I can think of for you to do while you are away from your home ISP. Sorry.
Marilyn