Outlook Express PW

For whatever, OEx quit recognizing my PW completely.
Went to IExplorer to get to account (I usually use T'bird), and had to reset PW.
OEx mail through IExplorer accepted change or reset.
Went back to T'bird to access email, but now I cannot send as the SMTP does not recognize old or new PW. I can recieve.
How would I find whatever is stopping or doing this and get my account back up and sending as well as receiving?
Thanks,
Skysarge
Will check back in tomorrow)