A shared mailbox normally does not need its own licence if it stays within 50 GB and does not need features requiring additional licensing. The people accessing it still need their own licensed Exchange Online mailboxes.[1] That distinction matters when you are deciding whether a reception, accounts or enquiries address needs another paid subscription.
Check the mailbox’s size, purpose and required features before removing anything. A shared address is not a way to give several employees unlicensed email accounts. This guide covers the mailbox-specific decision; our Microsoft 365 renewal guide covers the wider subscription review and the instructions to send your supplier.
Separate the shared address from the people using it
Microsoft describes shared mailboxes as suitable for addresses used by several people, including support and reception teams.[1] Think about who needs to read incoming messages and who should reply. Name a business owner for the address so requests for access do not depend on whoever happened to set it up originally.
Write down the people who need access, including occasional holiday cover. Ask your administrator to check their existing email licences rather than buying a second user subscription for every shared address. Review that membership when somebody changes role. Keep access to sensitive accounts or personnel messages limited to the staff whose work requires it.
Check storage before reclaiming a licence
The standard unlicensed shared-mailbox limit is 50 GB; Microsoft specifies Exchange Online Plan 2 to raise the mailbox limit to 100 GB.[1] Ask for the actual storage figure, not an estimate based on how busy the address seems. Record when it was checked and agree who will monitor growth afterwards.
Do not delete old correspondence simply to get below a licensing threshold. Ask the information owner what must be kept and whether an archive is needed. If the mailbox is already close to its limit, ask your provider to compare the supported options before making a change. Include expected growth from attachments and incoming documents in that conversation.
Treat archiving and compliance as separate questions
Archiving, litigation hold and advanced security or compliance features can change the licensing requirement.[1] Ask your administrator to identify the features actually enabled or required for this mailbox, then confirm the necessary licence combination against Microsoft’s current guidance. Avoid treating the storage limit as the only test for whether a licence can go.
Bring any existing retention instructions into that review. Ask the person responsible for the information to explain what the business needs to preserve and why. Keep those requirements separate from a general wish to save subscription costs. Where the answer is uncertain, leave the licence decision open until the technical and information owners have agreed it.
Convert a leaver’s mailbox in the right order
Microsoft says a user mailbox needs a licence before conversion to a shared mailbox, and that conversion retains its email and calendar information.[2] Ask your administrator to plan the handover before reclaiming the licence. Confirm who will handle incoming work and whether keeping the old address active is still appropriate.
Do not delete the associated account: Microsoft says it anchors the shared mailbox.[2] Conversion also needs a separate access-security check. Microsoft warns that the original credentials can continue working after conversion, and its shared-mailbox guidance says direct sign-in must remain blocked.[1][2] Have the administrator verify that control rather than assuming the change of mailbox type removed access.
Test reading and sending separately
Full Access lets a delegate open the mailbox, but sending requires Send As or Send on Behalf permission as well.[3] Ask the business owner which behaviour is appropriate. A colleague who only needs to review messages should not automatically receive every available permission. Record the agreed access alongside the mailbox’s owner and purpose.
Test the result with the staff who will use it. Ask them to open the mailbox, receive a test message and send an authorised reply. Check the sender shown to the recipient and agree how colleagues will avoid answering the same enquiry twice. Include holiday cover in the test instead of discovering a missing permission when the usual contact is away.
Confirm what changes on the invoice
Removing an assigned licence does not itself stop payment for the subscription seat; Microsoft’s setup guide explicitly separates those actions.[3] Ask your supplier when the purchased quantity can change and what confirmation it needs. Keep the technical change record separate from the billing instruction, with an owner for each.
For a practical review, bring the mailbox address, storage figure, access list and required features to your Microsoft 365 support conversation with BMT. Agree whether to retain, change or remove the mailbox’s licence, then check access and billing after the approved change. That gives you a decision you can verify rather than an unexplained reduction in the licence count.
Sources
[1] Microsoft: about shared mailboxes