The error is caused by how the Google (Gmail) account is connecting to Outlook, not by anything that needs developer skills. Use these steps that are supported for Outlook and Gmail.
- Make sure IMAP is enabled in Gmail
- In a browser, go to Gmail.
- Select Settings (gear icon) > See all settings.
- Open the Forwarding and POP/IMAP tab.
- Under IMAP access, select Enable IMAP.
- Select Save Changes.
- Check that Outlook is using the supported Gmail connection
For Outlook.com / Outlook on the web, use the standard Gmail IMAP/SMTP settings:
- Incoming mail (IMAP) server:
imap.gmail.com, SSL required, Port 993 - Outgoing mail (SMTP) server:
smtp.gmail.com, SSL required, TLS if available, authentication required, Port 465 (SSL) or 587 (TLS/STARTTLS) - Username: full Gmail address
- Password: Gmail password (or app password if using that)
- Incoming mail (IMAP) server:
- If Outlook classic is used and signāin fails
- There is a known issue where adding or syncing Gmail in classic Outlook can fail with IMAP or signāin errors.
- This has been fixed in newer Outlook builds. Ensure Outlook is updated to a build that includes the fix.
- If IMAP is not enabled in Gmail (step 1), Outlook will also show an error that the Google account cannot be set up with IMAP.
- If the browser or app is reported as ānot secureā or signāin page looks wrong
- The Outlook fix changes signāin to open in another browser window. Make sure Outlook is updated to one of the listed fixed builds (for example, Version 2404 Build 17531.10000 or later on supported channels).
If the problem continues after enabling IMAP and confirming the IMAP/SMTP settings, update Outlook to the latest version available for the account and then remove and reāadd the Gmail account using the standard Gmail option.
References: