cannot access mac.com email

hello everyone!

i was just wondering if someone can please help me out. i cannot go to mac.com email. something pops out that is says something like this:

The SMTP server smtp.mac.com rejected the password for user belcantotenoresupremo
Please re-enter your password, or cancel.

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what do i do? i have been entering the right password for hours and hours and hours and it is not working.

thanks for your help guys!