Will the migration create duplicates between the primary and archive mailboxes? (4348337)

On Demand Migration (ODM) and On Demand Migration for Email (ODME) are designed to not duplicate mail items between primary and archive mailboxes regardless of the source or target mailbox type. This design ensures that items will not be duplicated in the target even if source mail has moved from the primary mailbox to the archive mailbox between migration jobs.

For Example:

If you migrate from a source primary mailbox to an archive mailbox, then later decide you want to migrate that same source primary mailbox to a primary mailbox instead, ODME will see that the data has already been migrated to the archive mailbox in the target and will skip the mail items that have already been migrated.

If you are performing a muti-pass migration and migrate a source primary mailbox to a target primary mailbox, then after that initial migration, data is moved to the archive mailbox in the target, the data will not be duplicated on subsequent migration passes.

NOTE:
There is a known scenario, in which the mail sync will not be applied:
If you ran a Mailbox Migration from Primary to Primary, our tool scans Target Primary and Archive to find previously migrated mails. If you run mailbox migration from Archive to Archive, we do not scan Target Primary mailbox for previously migrated mails, as the mails cannot go from Archive back to Primary in a "natural way". It can be done manually, but we think it's a rare case, and this is something that can caused duplicates.