Applying Retention Policy to Delete Emails from Specific Sender for All Users

Question

I need assistance with a specific use case. We have an SMTP address in our organization that sends bulk emails to all users, and I’d like to ensure these emails are deleted after 3 months for all recipient inboxes. This requirement includes both new and existing emails from this sender across all mailboxes.

I want to apply a retention policy that automatically deletes all emails from this specific SMTP sender after 3 months for all users in the organization.

The policy should apply to both new emails and any existing emails already received from this SMTP address.

Ideally, I’d like to avoid manually tagging older emails, if possible, and have the policy retroactively apply to all messages from this sender.

I have explored using a mail flow rule to add a custom header to incoming emails from the sender, and I can apply a retention label with a 3-month deletion policy using this header.

However, I am unsure how to handle existing emails that do not have this custom header, as they were received before the rule was implemented. I am also trying to avoid using Content Search and Purge in the Compliance Center, as it has limitations (deleting only 10 items at a time) and is not practical for bulk deletion across all mailboxes.

Questions:

1. Is there a way to enforce the retention policy retroactively to delete all messages from the SMTP sender across the organization without relying solely on the custom header?
2. Alternatively, is there a recommended method to tag older emails from this sender so the 3-month retention policy will apply?
3. If there is another approach or tool within Microsoft 365 that can better meet these needs, please advise.

Answer 1

Hi @Aarushi Rajput
Welcome to Microsoft Q&A platform and thanks for posting your query here.

It seems like you're looking for a way to apply a retention policy to delete emails from a specific sender for all users in your organization. I'll do my best to help you out.

Based on the information you provided, it seems you've explored using a mail flow rule to add a custom header to incoming emails from the sender, and then applying a retention label with a 3-month deletion policy using this header. However, you're unsure how to handle existing emails that do not have this custom header.

Is there a way to enforce the retention policy retroactively to delete all messages from the SMTP sender across the organization without relying solely on the custom header?

Unfortunately, there is no way to enforce the retention policy retroactively to delete all messages from the SMTP sender across the organization without relying solely on the custom header. The retention policy is applied based on the retention label, which is applied to the email based on the custom header. Without the custom header, the retention label cannot be applied, and the retention policy cannot be enforced.

Alternatively, is there a recommended method to tag older emails from this sender so the 3-month retention policy will apply?

One approach you can take is to use a Content Search in the Compliance Center to search for all emails from the specific sender, and then apply a retention label with a 3-month deletion policy to the search results. This will tag the older emails from the sender so that the retention policy will apply.

To do this, follow these steps:

• In the Microsoft 365 Compliance Center, go to Content search.
• Create a new search and specify the search criteria to find all emails from the specific sender.
• Preview the search results to ensure that the correct emails are being returned.
• Apply a retention label with a 3-month deletion policy to the search results.
• Wait for the retention label to be applied to the search results.
• Monitor the retention label to ensure that it is being applied correctly.

If there is another approach or tool within Microsoft 365 that can better meet these needs, please advise.

Unfortunately, there is no other approach or tool within Microsoft 365 that can better meet these needs. The Content Search and Purge in the Compliance Center is the recommended tool for bulk deletion across all mailboxes.

Appreciate if you could share the feedback on our feedback channel. Which would be open for the user community to upvote & comment on. This allows our product teams to effectively prioritize your request against our existing feature backlog and gives insight into the potential impact of implementing the suggested feature.

I hope this helps! Let me know if you have any further questions.

Answer 2

Mail flow rules can only process new messages, existing items will not be affected. However, you should be able to use a query-based auto-apply (retention) policy, with the criteria you outlined. The details on how to configure such policy are here: https://learn.microsoft.com/en-us/purview/apply-retention-labels-automatically#auto-apply-labels-to-content-with-keywords-or-searchable-properties

Do note that this functionality requires the E5 SKU.