When creating a Teams migration tasks, under Channel Posts (Messages) there is checkbox that allows posts to be archived.
Archive - Migrate and archive channel messages as an HTML file for each channel. The HTML file is added to the file list of the team's SharePoint site in the target tenant. A new message from the target tenant Administrator is added to each migrated channel with a link to its HTML file. A new tab called Conversation History is created in the target channel and the archived messages are displayed there.
- All messages - Migrate and archive all messages across all channels in the team.
- Messages older than 15 days - Migrate and archive messages across all channels in the team that are older than 15 days.
- Messages older than 30 days- Migrate and archive messages across all channels in the team that are older than 30 days.
- Messages older than 60 days - Migrate and archive messages across all channels in the team that are older than 60 days.
Note:
Messages that are more recent than the 15, 30 or 60 days option that is selected will be migrated but not archived.
If the migration task is successful and the archive HTML file is created in the target tenant, it cannot be modified by subsequent migrations. If you attempt another migration and select the Archive option, the Archive option is ignored. All new and modified channel messages from the selected teams will be migrated and posted to the corresponding team channels in the target tenant. Messages already archived will be skipped unless they were subsequently modified (edited or linked to replies or attachments) in the source tenant.
If the migration task is unsuccessful and the archive file is not created, subsequent migrations with the Archive option selected will attempt to create an archive HTML file in the target tenant. Archive sub-options like All, Messages older than 15 days, Messages older than 30 days or Messages older than 60 days, are re-evaluated for all messages in the channel. The new set of messages selected for archival may not be the same set of messages identified in the previous archive attempt.
