A few days ago, someone on the Central West End Linux Users Groups asked a good question:
We are staying with relatives for the next few months and they have DSL but the provider, htc.net, is blocking port 25 for any outgoing server other than their own. I've tried to use other ports to send mail via our company's server, comcast.net, but to no avail.
My response? Use Gmail. When my correspondent indicated that he didn't know how to do that, I wrote the following.
Set up a Gmail account if you don't already have one, at http://www.gmail.com
In Gmail, go to Settings > Accounts.
Where it says Send Mail As, click Edit Info.
In the Edit Email Address window, change (a) Name to something you want to use if the default isn't correct, and (b) Reply-to Address to the name & email address you want email recipients to see & reply to. Mine, for instance, says:
Scott Granneman <firstname.lastname@example.org>
Press Save Changes to close Edit Email Address.
In Send Mail As, make sure that "Reply from the same address the message was sent to" is checked, as that way, if someone emails you specifically at your Gmail address, you will reply from that, but if they email you to the address you're setting up as the Reply-to, that will be used instead.
Now, in your email client (Thunderbird, Evolution, etc.), go to wherever you set up SMTP. You need to add/change settings for Gmail's SMTP. Secific instructions are available for your client in Gmail's help, but here are the generic instructions.
Server name: smtp.gmail.com
Secure connection: TLS
Authenticate with your gmail address as your user name
Authenticate with your gmail password as your password
Try sending an email to yourself using your Gmail SMTP. The bonus to this is that all SMTP between you & Gmail is encrypted, so no snooping by others when you're sending mail.