Can not get into my smtp because I can not remember password.

I have never used my .mac account for mail. I have a hotmail acct that I want to continue to use but, when I want to send an e-mail from certain sites, ( like my daughter's school account), it automatically grabs my mac account of which I can not even get into because I can't remember my passcode. How can I get my mail to all come and go from only my hotmail acct.. It is so frustrating because I can not ask any questions or get responses when it goes into my mac acct.. ugh! would appreciate any help...