Trouble with Mac-mail, after returning from vacation.

After getting back from the U.S. my Mac e-mail is not allowing me to save changes to the account settings. I changed my password, and it seems fine for incoming e-mail, but not outgoing. It shows 'outgoing offline'! Retyping my password (to make sure it's correct) I get a message "Unable to Verify account or password"?? Obviously with my incoming e-mail working fine (and showing it's online) why do I get this message? It states in the support help of my Internet company, to just have my name (in the username field) but my whole e-mail address is in there...which worked just fine up to going on vacation, as well as the full time being away, but after changing it just to the username without the @---.ca I get a message "A SMTP account already exists. Only a single SMTP account is allowed". I've closed the Macmail application numerous times, rebooted the MacBook, and oddly...did a simple test, sending a very minimal test e-mail...and it sent, thinking all was fine, but that's not the case as it still shows as being 'outgoing'...offline. Other e-mails sitting in the Draft folder, won't send, as I just get a box asking for my password, but I then get the first message mentioned above!

I've heard of others having similar issues in the past, but when asked what they did, they (like me) had it happen in years passed, and can't remember the fix! Would appreciate any help on this...thanks!