Mail - Can't send email but can receive it?!?!?

I've been using Mail for about a year now, and up until last month it was working fine.

For some reason, without altering any settings (to my knowledge) I can no longer send email. My outgoing mail server has always been 'smtp.gmail.com', and now it no longer works.

I hear that there have been similar problems involving GoogleMail and Mail.

If anyone could give me any clue as to what the problem could be I would be very grateful.

Go into Mail preferences, Accounts, and make sure Outgoing Mail Server is set up correctly. Sometimes by default a number of options are available and have seen wrong option selected.

If all is well try running Repair Permissions.

Make sure the port is either 465 or 587