Good questions. I have a few introductory/background points before I respond to the questions directly.

For those who may be unfamiliar with how retention works with MS Teams, have a look at these two related sites.

The quote below from the second link is relevant to this post:

'Teams chats are stored in a hidden SubstrateHolds folder in the mailbox of each user in the chat, and Teams channel messages are stored in a hidden SubstratesHolds folder in the group mailbox for a team. Teams uses an Azure-powered chat service that also stores this data, and by default this service stores the data forever. With a Teams retention policy, when you delete data, the data is permanently deleted from both the Exchange mailboxes and the underlying chat service.'

and

'Teams chats and channel messages aren't affected by retention policies applied to user or group mailboxes in the Exchange email or Office 365 groups locations. Even though Teams chats and channel messages are stored in Exchange, they're only affected by retention policies applied to the Teams locations.'

In summary:

One-to-one chat in MS Teams is stored in a hidden folder of the mailbox of each user in the chat. Documents shared in those chats are stored in the OneDrive for Business of the person who shared it.
Group chat in Team channels is stored in a hidden folder of the mailbox of the associated Office 365 Group - and also in an Azure chat service. Documents are stored in the Office 365 Group's SharePoint site (other SharePoint site libraries may also be linked in a channel).

Another quote from the same post:

'In many cases, organizations consider private chat data as more of a liability than channel messages, which are typically more project-related conversations.'

Typically, in the on-premise past, organisations will have backed up their Exchange mailboxes (and possibly also enabled journaling, to capture emails), for disaster recovery, 'archiving' and investigations. Unless a decision is made to invest in cloud back-ups, Office 365 retention policies may also be applied to Exchange mailboxes, effectively replacing the need to back them up. Retention policies applied to Exchange mailboxes don't affect the teams chat folder.

My sense is that organisations should apply the same retention period to both emails and Teams chats as they do to email mailbox backups now. If mailboxes are typically kept for 7 - 10 years after the person leaves the organisation, then keep the Teams chats for the same period.

Note that, even if a poster deletes an item (if that option is enabled), it will still be retained if there is a retention policy.

To your specific point about the potential for different retention requirements, depending on the subject matter, my thoughts are:

One-to-one chat is like email, you will never know everything that is being said or sent. So a single retention policy that mirrors email would be appropriate.
Teams chat is more likely to be about the subject of the Team, which is based on an Office 365 Group, its own mailbox, and has a SharePoint site. In this case, you could consider a retention policy applied to all Office 365 Groups or specific Groups - for example 'Project Groups', then ensure that the retention policy or policies cover all aspects of the Office 365 Group (mailbox, team chat, SharePoint).

If all your project records (including email, chat and documents) must be retained for 25 years, then you need to understand all the options.

It underscores the need to plan carefully for retention management for all the key workloads in Office 365.

Andrew Warland
Melbourne, Australia

On Wed, Feb 19, 2020 at 10:52 PM Donald Henderson - CHX <[log in to unmask]> wrote:

We are currently struggling with MS Teams chat (including ‘conversations’) and the idea of applying a global retention policy to it and I’m just wondering how anyone else has addressed it.

My initial idea was that chat is basically ‘immediate’ and should have a short retention period. I suggested a month and was willing to extend that to 6 months in the face of serious opposition.

It has now been suggested to me that some sections of the organisation will actually post ‘important stuff’ in chat – the example being quoted was interactions round a major capital building project, including with the contractor. My thoughts are that this sort of stuff starts to warrant retention as a record of the capital project, i.e. 25 years and possibly permanent retention depending on the project.

Since it is really hard to get rid of individual items of chat (only the poster can delete their own posts), this raises the spectre of retaining every item in a Team site for the entire retention period. The thought of a subject access request or, probably worse, an FOI request for all the stupid GIFs that have been posted is just a bit concerning.

So, how do you manage chat?

Donald

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