Many times I have missed a possiblity to send mail so that I set up the sending SMTP server only once. Currently I have to change it every time I change my connection from work to home or mobile. Finding a suitable SMTP server is not a trivial task. Operators want to protect their servers from spammers and unpaying customers. The names are not standard and ports, encryption and authentication varies.
Just today I realized that it has been there likely for some time. Gmail account allows sending mail using their SMTP server. Just set your setting to smtp.gmail.com, use SSL and port 993. You have to use your gmail account as user name (don’t forget @gmail.com) and gmail password.
This is not advertised much but if you go to document expaining IMAP settings for e.g. Thunderbird, it is there.
Of course, you have to think if you want Google to see even your outgoing mail. Thunderbird + Enigmail recommended for encryption.
I always recommend IMAP over POP. I use much more clients to access mail than I have mail accounts. POP is meant for downloading mail from many accounts to one place where you keep all your mail. IMAP is meant to access mail from remote storage. If you have mobile mail access or you use many clients, you want IMAP. If you have a nice super storage server like gmail, you want IMAP.
Therefore, I find it extremely strange that Thunderbird 2 has a Gmail mode that is hardcoded as POP. If you want to use Gmail using Thunderbird, forget the built-in Gmail account type and just use generic IMAP account settings.
And voilá, your gmail account is just like any other.