DMS IMAP migration silently skipping emails & delta counts are inconsistent. Already cut over. What now, and should I switch to GWMME for the rest?
Hey guys,
Need some advice from people who dealt with this before.
Just finished migrating a domain from a legacy IMAP server to Google Workspace using the built-in Data Migration Service (DMS) in the Admin Console. The cutover is already done—MX records are changed, users are working, incoming mail is live on GWS.
Here is the mess: DMS report showed some skipped items as spam/virus, which is fine. But users started complaining about missing old emails (inbox, sent, subfolders). We checked, and DMS silently dropped a bunch of legit emails without showing any error in the console.
We ran delta migration multiple times. Every single time delta finishes, the migrated/scanned numbers don't match the previous run. It's completely inconsistent. Because the mailboxes are now live with new incoming traffic, old and new emails are mixed up, and we can't just keep running delta blind hoping it catches everything.
Two questions:
- How do we fix the current live domain? Is there a reliable way to audit what is missing between the source IMAP and GWS without blowing up the live inboxes or creating duplicate emails? If I run an external tool against the live mailboxes, does GWS handle deduplication properly based on Message-ID, or will it create duplicates/duplicate labels?
- What about the next domains? I have a few more domains to migrate from the same source environment. Running DMS again feels like a trap. Is GWMME (Google Workspace Migration for Microsoft Exchange) in IMAP mode significantly more reliable than DMS? Does it provide actual granular failure logs (like exact message UID/Subject that failed) so I don't deal with silent drops again?
Any battle-tested workflow or tool recommendations (GWMME, imapsync, etc.) would be appreciated. Thanks.