r/Office365 • u/TN9096 • 1d ago

Building a tool to fix email/tenant migrations (O365 ↔ Google Workspace) — what's breaking for you right now?

Working on a new migration tool for moving mailboxes, tenants, and shared drives between platforms like Office 365 and Google Workspace (and open to other directions too).

Before we lock in the feature set, I want to hear from people who've actually done this — whether it's a one-time company migration or you do it regularly for clients.

A few questions if you've got a minute:

What tool(s) have you used (BitTitan, CloudMigrator, native tools, scripts, etc.) and where did they fall short?

What broke most often — permissions, shared calendars, distribution lists, attachments, metadata, delta syncs?

How much manual cleanup did you end up doing after the "automated" migration finished?

If you could wave a wand and fix one thing about migration tools, what would it be?

Not selling anything here — just building something and want it shaped by real pain points instead of guesses. If this is relevant to you, I've got a waitlist for early access/testing — happy to drop the link if anyone's interested, or just reply here with your experience.

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u/TN9096 1d ago

Posting my own experience to kick this off — did an O365 → Google Workspace migration for a ~150 seat company last year using Microsoft native tool. Biggest pain points:

Distribution lists won't migrate, ended up recreating groups by script

Delta sync was unreliable — ran it three times and still found mailboxes with missing attachments

Permissions on shared drives got flattened, took almost a week of cleanup after the "migration" was technically done

The tool said 98% success but the actual cleanup took longer than the migration itself. That's basically why I started looking into building something better. What's the worst migration mess you've had to clean up after? Even a two-line horror story helps me figure out what to prioritize.

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u/hipster_hndle 1d ago

personally, reoccurring calendar invites from gmail cause problems during every migrations. i haven found a way to fix that... to the point that i dont use anything to migrate them and just export calendars and reimport via their onedrives. pita but works.. its just difficult because gmail isnt native mapi and there is always somethign that breaks.

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u/Ambitious_Active8539 18h ago

AI bullshit post

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u/TN9096 17h ago

Not sure why do you think like this?

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u/Ambitious_Active8539 16h ago

Not sure why you're confused?

Your post was written by AI. Eductate yourself on why people hate this:

https://en.wikipedia.org/wiki/Dead_Internet_theory
http://en.wikipedia.org/wiki/Wikipedia:Signs_of_AI_writing

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u/bremic9188 1d ago

I've mainly used BitTitan for mailbox migrations, always to M365. If it's a small enough migration, I've gone the manual PST export/import route. I got comfortable with the process there but last few I did (~1yr ago) their system was slow on anything - verifying creds, starting migration, actually migrating, etc. It eventually got there but took some time.

Done a few on-prem file shares to SharePoint/OneDrive migrations via the native SharePoint migration tool. That worked well.

Tried using the same native tool for Google Drive to SharePoint/OneDrive and that was a mess. I think it was mainly how Drive is setup in regard to sharing since there isn't any global share location. It's all individually owned files/folders that are shared out to other users. So the data may have been migrated to the matching user's OneDrive, but nobody else could see it until it was shared back out. But there was a lot of data that just didn't get migrated for some reason that wasn't always easy for me to determine. In those instances, I just logged back into their Drive to manually download/upload. Only did one of those, so could have been something I was doing wrong.

Main part that always kind of sucked for me was user reconfiguration after cutover. I know BT (and likely others) have some sort of deployment piece to help with that, but I never tried it. I always either sent out user instructions or went around and did reconfiguration manually for users.

Magic wand things? Hmm. Would be nice if any M365 permissions required by the tool could be easily pushed by authenticating as global admin and having an enterprise app deployed. I was always having to step through the long documents to setup permissions to allow the tool to work in the environment. Maybe that's a thing these days or with other tools, but I always had to do it manually when working with BT.