If you use the same computer at more than one location, with more than one
Internet connection you certainly know the problem: every connection needs
its own outgoing mail server, because every ISP only accepts mail from their
own users. This means changing the SMTP server settings in your email client
every time you switch connections.

The much easier and efficient alternative? Run your own outgoing mail
server. With Mail Express, this is not nearly as difficult as it sounds.
Install the utility, change your outgoing mail server to "127.0.0.1" (once!)
and use email like you did before. Mail Express accepts the mails you send,
and if you are connected delivers them directly to the recipient bypassing
any other mail server.