If you are receiving an "Incorrect password" error in the e-mail program on your local device (computer, phone, tablet, etc.), but you are sure that you have entered the correct password, please check your e-mail username as well.
The username that you should use in your e-mail program must be YOUR FULL EMAIL ADDRESS, and not only the part before the @ sign. For example, if your mailbox is johnsmith@example.com, then the username must be johnsmith@example.com, and not just "johnsmith". If you use just "johnsmith", then you might see an "incorrect password" error.
Also, please make sure that there are no whitespace characters entered before or after the password in your e-mail program.
Full instructions on configuring the most popular email programs can be found in the Configuring an e-mail program (Outlook, Thunderbird, Mail, etc.) section of the FAQ.