What Does Not Migrate: Permissions, Public Folders, Shared Mailboxes, and Calendars
A field guide to the objects and relationships that mail and Drive migrations silently drop — so you can plan workstreams instead of discovering gaps on Monday morning.
- Messages moving is not success. Delegates, room calendars, and sharing links are the surprise losses.
- Public folders and some nested permissions have no perfect one-click mapping.
- Google Shared Drive membership is not the same as NTFS or Exchange ACLs.
- Build an explicit ‘exceptions backlog’ before cutover, not after users complain.
Migrations fail at the edges
Tools advertise “mail and files.” Users live in relationships: who can send as whom, which room is bookable, which Shared Drive managers can delete. Those objects are where projects lose trust even when item counts look perfect.
Mail: what commonly does not follow
- Full Access / Send As / Send on Behalf — must be re-granted on the destination identities.
- Delegates and Outlook folder permissions — especially nested folders.
- Public folders — need a dedicated strategy (mail-enable, Microsoft 365 Groups, SharePoint). They are not “just another mailbox.”
- Shared mailboxes vs user mailboxes — converting at the wrong time drops the address or the history. Move them as named objects with owners.
- Room and equipment mailboxes — booking policies, delegates, and add-in settings rarely copy cleanly.
- Litigation holds and archive mailboxes — online archives can require extra steps; holds are compliance, not a folder.
- Client-only artifacts — local PST, NK2 autocomplete, some categories, POP leftovers.
IMAP as a source drops even more: calendars, tasks, and ACLs are not IMAP’s job. If the source is IMAP, schedule a calendar workstream on day one.
Calendars and contacts
A meeting is not just a time. It is attendees, rooms, attachments, and whether the new system still knows the room mailbox. Cross-platform moves (Google ↔ Microsoft) routinely break rooms and recurring series. Export a month of board meetings and recreate rooms on the destination as a test, not as a hope.
Personal contacts vs GAL vs delegated contacts: users will call “my contacts vanished” when they meant the old company’s address book. Teach the difference in the comms plan.
Files: Drive and SharePoint
- Sharing links (anyone with the link, company link) usually die across tenants.
- Google Shared Drive roles (Manager, Content manager, Contributor) do not map 1:1 to SharePoint groups.
- Shortcuts vs files in Drive — a shortcut that migrated as an empty pointer looks like data loss.
- Version history is often truncated or reset on move.
- Externally shared items — partners lose access until you rebuild.
Build an exceptions backlog
Two weeks before cutover, list: every shared mailbox, every room, every public folder, every Shared Drive with external users. Assign an owner. Mark “migrate / rebuild / retire.” Anything unmarked will become a Monday ticket.
Verification is not only item counts. Sample: send-as a shared mailbox, book a room, open a partner link, open a recurring meeting. Those five tests catch more pain than a 100% message-count report.
Related reading
Choose the move pattern with cutover vs staged vs hybrid vs IMAP. For Exchange/IMAP mechanics, see migrating Exchange or IMAP to Microsoft 365.
