In classic Outlook, the Gmail account was likely configured as an IMAP account, and the “files” (folders) used for filing messages were server-based IMAP folders. When a message was moved from the Gmail Inbox to one of those folders, the move happened on the server, so the message disappeared from Gmail webmail and other clients.
In New Outlook for Windows, Gmail accounts are synced to the Microsoft Cloud and the behavior is different:
- IMAP only supports mail, and New Outlook uses a cloud-sync model for non-Microsoft accounts such as Gmail.
- Folders that are local-only (stored “on this computer”) are not Gmail/IMAP folders. Moving a message from a Gmail folder to a local-only folder removes it only from the local Outlook data, not from Gmail on the server.
- On the next sync, Gmail still has the message in the Inbox, so it reappears in New Outlook and remains visible in Gmail webmail and on the iPhone.
To have messages disappear from Gmail everywhere, they must be moved into a folder that exists on the Gmail server (an IMAP folder/label that is set to “Show in IMAP”), not into a local-only folder. With New Outlook’s cloud-sync architecture, using local-only folders for a Gmail account will not propagate deletions or moves back to Gmail.
If the goal is for messages to drop out of Gmail in all locations, use server-based Gmail folders/labels (visible in IMAP) for filing instead of local-only folders. Local-only storage of Gmail messages in New Outlook will not sync those moves back to Gmail.
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