Mac Mail problem

I use only 1 email address - its a pop3 a/c.

However, i have a blackberry and in order to get a copy of my outgoing blackberry emails, i send a bcc copy to a gmail a/c. And then i have set up a gmail a/c on my Mac Mail to download those messages.

In the ACCOUNTS - account information tab

outgoing mail server pop3/entered correctly gmail/none
use only this server pop3/checked gmail/unchecked

advanced tab
enable this account pop3/checked gmail/unchecked

Problem is that when i compose a message at random, the mac mail sends out the message using my gmail id ... its really funny - i dont know how and why it does so.

When i compose the message, on the server tab its clearly showing my pop3 server. but when i check the sent message, its showing the gmail id.!!

a) How do i completely disable gmail from sending messages? (i even tried to enter a wrong outgoing server name... it still sends out..!)
b) Is there a better way to save outgoing blackberry emails on desktop?

Any help appreciated. Thank you.