Symptoms
When you use IMAP to connect to your email account in classic Outlook for Windows, authentication fails.
Cause
This issue may occur because your password contains a Unicode character, such as ä, ö, or ü.
Workaround
To work around this issue, use one of the following methods.
Method 1: Change your password
Change your password so that it no longer contains any Unicode characters.
Method 2: Use POP instead of IMAP
If your email provider supports POP, you can set up the account as a POP account instead of an IMAP account.
Note
With POP, Outlook downloads messages to your computer and, depending on your settings, may remove them from the server. With IMAP, messages stay on the server. For more information, see What are IMAP and POP?.
In classic Outlook, select File > Account Settings > Account Settings.
Select the IMAP account, select Remove, and then select Yes.
Note
If the IMAP account is the only account in Outlook, you're asked to create a new location for your data before you can remove the account. For more information, see Create an Outlook Data File (.pst) to save your information.
Select File > Add Account.
Enter your email address, select Advanced options, select the Let me set up my account manually check box, and then select Connect.
Select POP.
Enter the incoming and outgoing mail server settings for your account, and then select Next.
Note
Go to your email provider's website or contact them to get the incoming and outgoing mail server details. Common settings are listed in POP and IMAP email settings for Outlook.
Enter your password, and then select Connect.
For more information, see Add an email account to Outlook for Windows.