I am posting this as much for information and if anyone has any comments. The issue arose from a question from someone asking if it is possible to have different retention policies for MS Teams chats - or even just one - where one retention policy would delete only one side of the conversation.
For example, person A is chatting with person B. Person A's chats are covered by a 30 day retention (includes that person in the settings), but Person B's chats are covered by a longer retention (or none at all).
What happens at the end of the 30 day period, does it delete just Person A's chats, or both, or none?
To find out, I created two retention policies for MS Teams chats (not channel chats):
(a) a 30 day policy for everyone except Person A;
(b) a 2 day policy for only Person A.
Then I exchanged chats between Person A and another person. After the 2-day retention policy expired, the chat messages from or to person A were deleted for everyone (no longer visible to either side). However, as the chat messages were subject to a longer retention policy, I could still find and access them (for the remainder of the retention period) via Content Search in the Compliance portal.
So, it seems that any retention policy will remove both sides of the chat but if the chats are subject to a longer policy, the chats will still be retained for that longer period.
Has anyone found a way to avoid both sides of the chat being removed?
