If you travel widely and rely on a laptop and an email client for picking up your email then you may have experienced some trouble in sending your messages because of anti-spam procedures put in place by air time providers.
What the majority of Internet service providers do is block all traffic to port 25 unless that traffic is directed at one of the service providers’ servers. So, if you use an e-mail client (as opposed to webmail) such as Outlook or Thunderbird, and are travelling and/or connected to a different network than you’re used to, you might not be able to send e-mail.
One way of working around this is contained on the rather wonderfully named Peter’s Useful Crap (which has the sub line “Giving you as much crap as possible. Good crap, though. Useful crap”) – well it is useful if you use one of the providers he uses for examples or you expend a little brain power using other workarounds and changing the port 25 smtp server details.
A far simpler and elegant way of getting around port 25 blocking is to use Loa PowerTools which I took at look at some months back (link).
The Loa site explains: “Loa PowerTools is a tiny utility that lets you send email from any internet connection anywhere. Once it is installed, you don’t have to change your life at all. You can use whatever email software you prefer: Outlook, Mac Mail, Thunderbird … it doesn’t matter, but Loa PowerTools will send your mail out through the Internet in a way that can’t be stopped by any but the most aggressive firewalls. And by “aggressive” we mean firewalls in secure places where you wouldn’t expect to be able to have much Internet contact with the outside world.”
Prices range from the free option which allows you to send 100 emails a month through the Loa PowerTools server to the top of the range option which gives you 7500 posts a month for $20. There are also special deals for Gmail and MobileMe users which you can check out here.