I can't send/receive Hotmail on my iMac. My username and password are correct. What do I do next?

Thank you. I'm not sure if that solved the problem or not or if other factors played into it. I deleted all the entries for hotmail in my keychain (there were 10). It didn't seem to have an effect right away. I closed the Mail application and still had the lightning bolt next to my hotmail account. I tested it by sending myself an email to my hotmail account and it landed in my gmail folder for some reason, but it definitely said it was addressed to my hotmail address. Then when I clicked on the lightning bolt on the hotmail account, the bolt disappeared and the email landed in the proper place. Magic! I can't explain it but thank you for your suggestion. Maybe it just took some time for the keychain deletion to take effect. Anyway, it seems to be working now. I really need to stop using that hotmail account.