Teams Channel Posts
When a user is terminated from the source environment, their Teams channel post data will remain and will still show their name. Please see the blog post below for examples.
Teams Chats
Teams 1:1 Chats with the terminated user will remain for non-terminated users, but the terminated user's name will be replaced with "Unknown User". The terminated user will be removed from that chat and the previous chats will appear as "Just me" for the non-terminated user.
The information provided above is the native Microsoft 365 handling of terminated user data, as described in the following Microsoft blog post:: https://learn.microsoft.com/en-us/archive/blogs/skypehybridguy/microsoft-teams-what-happens-to-a-terminated-employee-and-their-conversation-history
What does this mean for the migration of this data using On Demand Migration (ODM)?
ODM will be able to maintain the original poster details within Teams channel posts.
In order to migrate Teams 1:1 chats with terminated users, the highlighted option below would need to be enabled. Additionally, the terminated user would not be added to the chat and would appear as "Unknown User". Careful consideration should be made to ensure that the "Migrate chats with unmatched users" option is desired for your overall migration project.
