I don't understand why this has only recently been happening but I cannot
send mail using smtp in ol 2003.

I am trying to send using my Yahoo account but the send receive says that it
is sending messages that are not actually in the outbox, e.g (bottom rh
corner of screen sending 2 of 3 messages when there are no messages there to
send) then after a short while it says error send receive.

My ISP is BT and apparently they block port 25 so I changed the port
settings (as recommended by Yahoo) to port 587 but I still cannot send from
within outlook.

I have configured my e mail account to the letter of the pop 3 settings as
described in the Yahoo tutorial, I can receive but not send.

The only temporary solution that seems to work only for a short while is to
create a new profile, this uses the default port 25 but it only works for a
few days then stops sending.

If this helps

I am using Norton online security
I have recently installed Spamfighter

Please help if you can,