The error is caused by how Outlook classic signs in to Google, not by POP vs IMAP in Gmail.
There are two main things to check/fix:
- Make sure IMAP is enabled in Gmail (Google is removing the toggle for some users, but if it still exists for the account, it must be on):
- In a browser, go to Gmail.
- Open Settings (gear icon) > See all settings.
- Go to Forwarding and POP/IMAP.
- Under IMAP access, select Enable IMAP.
- Select Save Changes.
- Update Outlook to a build that contains the Gmail sign‑in fix:
- The issue “We weren’t able to set up your Google account with IMAP. You may need to make changes to your Gmail settings.” is a known problem in classic Outlook.
- Microsoft released a fix that changes the sign‑in flow to open another browser window. The fix is available in these channels/builds:
- Beta Channel: Version 2404 (Build 17531.10000)
- Current Channel Preview: Version 2404 (Build 17531.10000)
- Current Channel: Version 2404 (Build 17531.10000)
- Monthly Enterprise Channel: Version 2407 (Build 17727.10000)
- Update Office/Outlook to at least one of these builds (or later) via File > Office Account > Update Options > Update Now.
If Outlook cannot yet be updated to a fixed build, use the Gmail web interface in the meantime, or switch temporarily to a channel that has the fix, then switch back after updating, as described in the classic Outlook article.
If the error persists even after updating and confirming IMAP is enabled, verify the IMAP/SMTP settings match Google’s documented values (server imap.gmail.com on port 993 with SSL, and smtp.gmail.com on port 465 SSL or 587 TLS) and that the correct Google sign‑in flow completes in the browser window that Outlook opens.
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