2025-03-22
tl;dr Make sure IMAP functionality is available/enabled in the account you want to pull from with Gmailify.
Since there is zero helpful debugging information and zero support in Gmail, I thought this might help someone running into the same issue as me. If you have a Gmail account, into which you'd like to fetch email from an Outlook/Hotmail account, you can use Gmail's "Gmailify" functionality (note: it's completely different to the service on gmailify.com) which will let Gmail pull messages from Outlook, rather than having to forward from Outlook to Gmail.
Having set this up, the status in Gmail's settings was stuck with a message saying "Not synced yet" (or thereabouts - I can't remember the precise message - it definitely didn't say e.g. "Last sync: Successful (2 minutes ago)" as it does now it's working). It was stuck like this for days.
What was the fix? It turns out that Gmailify just uses IMAP behind the scenes to sync to Outlook, which if I'd really thought about it was probably obvious. Since I rarely use Outlook, I had turned off POP and IMAP access in my account years ago. Turning IMAP back on and requesting another sync from Gmail was sufficient to get it working.