Retention functionality with Teams – how it works- Microsoft SC-400 Certification
By Isabella Morgan / September 10, 2022 / No Comments / IBM and Microsoft Exams
A timer job from the Exchange service continually assesses chat and channels after a retention policy is configured. The timer job can take up to 7 days to initially run. The content is shifted to the SubstrateHolds folder once the content’s retention period has expired. This concealed folder exists in every user or group mailbox and is utilized as a soft-delete location before permanent deletion.
The process flow taken by the retention policies for chat and channel messages depends on whether the policy is set to retain and then delete, retain only, or delete only. The following diagram shows the process flow for Teams chat and channel messages:

Figure 11.5 – Retention process flow for Microsoft Teams
There are two different process flows indicated by the and the in the diagram:
- In the case where a channel or chat message is modified or purged by the user during the retention period we can do the following:
a. Retain and delete: In this scenario, the initial message is copied (if modified) or shifted (if purged) to the SubstrateHolds location within 21 days. Once the retention period expires, the message is then purged within 2 hours.
b. Retain-only: A duplicate of the initial message is made in the SubstrateHolds folder within 21 days. Once the retention period expires, the message is purged within 24 hours.
c. Delete-only: Once the retention period has finished, the message is shifted to the SubstratHolds folder. This takes 7 days from the expiry date, after which the message is then purged.
- In the case where a channel or chat message is not deleted during the retention period we can do the following:
a. Retain and delete: After the retention period has expired, the deleted message is moved to the SubstrateHolds folder. This can take up to 7 days after the expiry date and then, after 24 hours, it is deleted.
b. Retain-only: The message will stay where it was originally located, and no actions take place before or after the retention period has expired.
c. Delete-only: The message is moved to the SubstrateHolds folder within 21 days and, after another 24 hours, it is deleted.
Due to Microsoft Teams storage being complicated, we need to consider multiple points when configuring Microsoft Teams retention policies:
- A Teams channel message’s location is required for retention of channel meeting messages, which are stored using the same method.
- A Teams chat location is required for retention of impromptu meeting messages, which are stored in the same way as group chat messages.
- A shadow mailbox exists in the tenant for guest users in a meeting that your organization hosts. This mailbox can be subject to a retention policy and all messages from the meeting are stored in the shadow mailbox and the user’s mailbox.
- Your retention policies cannot delete messages for an external user who is joining by using an account from a different Microsoft 365 organization as those messages are stored in that specific user’s mailbox in the other tenant.
You will also need to be aware of what happens to content for users when they leave the org:
- Documents and files: With Microsoft Teams, these have the same conduct as SharePoint Online and OneDrive for Business due to them being stored in the same location.
- Chat messages: These are stored in an inactive mailbox for users who leave the organization whose account is deleted and when the chat messages are subject to retention. The same retention policies that were placed on the user before they were deleted are still in place and the data can be viewed by utilizing an eDiscovery search.
- Channel messages: An Azure database and the mailbox of the team is used for the storage of channel messages posted by a user. This content stays unaffected when that user leaves the organization.
In this section, we have looked at retention policies in Microsoft Teams. You can use the same method for creating a retention policy as shown in the Configuring a retention policy for SharePoint Online and OneDrive for Business section of this chapter, with the only difference being that you select the relevant option in the Locations window. In the next section, we will take a closer look at recovering data in Microsoft 365, including Teams, SharePoint, and OneDrive.
Recovering content in SharePoint and OneDrive
Documents and files that are retained allow users to restore them from a specific time period as and when they are needed. In this section, we will complete small lab exercises and take a look at recovery options for OneDrive for Business, SharePoint Online, and Microsoft Teams.