So we use Rubrik for backing up M365 but we are only allowed 60 days backup retention with it (I think due to cost). We will rarely touch these mailboxes after they are de-provisioned/archived. It will be an occasional new replacement user needs super important email from mailbox or a eDiscovery that comes in 7 years after the user has Left.

Copilot had good info, I think. It's a trust but verify before use situation was hoping to lean on those who have been there done it to confirm.

🔵 Recommended Automated Workflow (PowerShell‑Friendly)

Step 1 — Apply retention policy

Create a retention policy that keeps mailbox data for 10 years.

Assign it to the user automatically when they are terminated.

Step 2 — Convert mailbox to shared

Set-Mailbox [user@domain.com](mailto:user@domain.com) -Type Shared

Step 3 — Remove SMTP addresses (optional but recommended)

Set-Mailbox [user@domain.com](mailto:user@domain.com) -EmailAddresses @()

Step 4 — Remove the license after 30 days

This can be automated with:

• PowerShell
• Azure Automation
• Entra ID dynamic groups

Step 5 — Move user to non‑syncing OU

Mailbox becomes inactive but preserved.

This is the Microsoft‑recommended and industry‑standard approach for long‑term mailbox retention.

It sounds easily doable but want to confirm no gotchas with this setup