RemoteShared mailboxes
A team inbox, not a shared password.
Shared mailboxes are the right tool for info@, accounts@ and leavers' mail, and one of the most neglected parts of most tenants. Here is how licensing actually works, how to set them up so the team can see every reply, and a nine-point health check.
Licensing and limits from Microsoft Learn, checked 31 October 2026.
- The 50 GB rule
- Setup that works
- Nine-point health check
Reviewed by Blake Bath, General Manager, on 31 October 2026.
Right tool
Four good uses for a shared mailbox.
And the setup each one needs.
Team inboxes
info@, sales@, accounts@, support@.
- Named access
- Send As
- Shared sent items
Leavers' mail
Keep a departed person's mail available to their manager.
- Converted
- Sign-in blocked
- End date
Role inboxes
Rostering, dispatch, on-call, where people rotate.
- Group access
- Rota changes
- Reviewed
Kept correspondence
Mail that must outlast the person who handled it.
- Retention set
- Hold licensed
- Backed up
Shared mailbox health check
How healthy are your shared mailboxes?
Tick what is true for every shared mailbox you have. The gaps come back in the order we would close them.
Tick what is true for every shared mailbox.
Where you stand
0of 9 checks in place
9 gaps to close.
- Direct sign-in is blockedEach shared mailbox has a real account behind it. Leave it open and it is a login nobody watches.
- No shared passwordA shared password can't be traced to a person or revoked for one.
- Access is given to named peopleYou can see and remove exactly who has it.
- Sent items stay in the shared mailboxOtherwise the team can't see who answered what.
- Under 50 GB, or licensedUnlicensed shared mailboxes stop sending at the limit.
- Licensed for any hold or archiveHold and archive features need a licence on the shared mailbox itself.
- Each one has a business ownerOwnerless mailboxes collect access and never get reviewed.
- Access reviewed at least quarterlyFormer staff often keep access to team mailboxes.
- Forwarding and rules checkedAttackers hide in shared mailboxes because fewer people watch them.
The rules
How shared mailbox licensing works.
| Situation | Licence needed on the shared mailbox | Note |
|---|---|---|
| Up to 50 GB | None | It stops sending when full |
| Up to 100 GB | Exchange Online Plan 2 | Plan 1 doesn't raise the limit |
| Archive | Plan 2, or Plan 1 with Exchange Online Archiving | Also enables auto-expanding archive |
| Litigation hold | Plan 2, or Plan 1 with Exchange Online Archiving | Plan before converting a leaver |
| Advanced security or retention | May need its own licence | Check the feature |
| People opening it | Their own Exchange Online licence | Always |
Make it work
Setup that lets the team work properly.
- Full Access and Send AsFull Access lets people read. Send As or Send on Behalf lets them reply as the team.
- Sent items saved in the mailboxSo everyone sees the reply, not just the person who sent it.
- Sign-in blockedAccess only through named people's own accounts.
- Retention set deliberatelyTeam mailboxes often hold records you need to keep.
- Signatures and auto-replies testedCheck what outside senders actually receive.
When not to
When another tool fits better.
- Avoiding a user licenceNot allowed. A shared mailbox is not one person's mailbox.
- Private help for one personUse delegation on their own mailbox.
- High-volume supportA help desk system gives ticket numbers and service levels.
- Unlicensed compliance needsIf it needs hold or archive, license it or use another approach.
Our view
Shared mailboxes are where forgotten access lives.
In most tenant reviews, the shared mailboxes are where we find open sign-in, a password on a sticky note, leavers who still have access, and forwarding rules nobody remembers. Attackers like them for the same reason: fewer people are watching.
The fix is quick. Block sign-in, give each mailbox an owner, review access each quarter, and check its size and licensing when a leaver is converted.
The order
Tidying shared mailboxes in five steps.
- Step 1List them
Every shared mailbox, its size and who has access.
- Step 2Block sign-in
On all of them, today.
- Step 3Name an owner
Who approves access and closure.
- Step 4Fix the setup
Send As, shared sent items, licensing.
- Step 5Review quarterly
Remove leavers, check rules.
Related guides
Microsoft 365 done properly. Mailboxes, groups and licences.
The decisions around shared mailboxes.
Get help your way
Six ways to reach us. Pick whichever suits you.
Helpdesk hours are Monday to Friday, 8am to 5pm AEST. On Advantage and above, emergencies get a response within 1 hour and outages within 2, with 24/7 best-effort escalation.
- Call 07 3114 2808
An engineer answers Monday to Friday, 8am to 5pm AEST. After hours, weekends and public holidays, Chip, our AI agent, answers on the same number or on 07 3180 0965, logs it and escalates urgent incidents to the on-call engineer.
Call now - Email the helpdesk
Send it to helpdesk@realbytes.com.au and a ticket is logged straight away, with a reference number you can quote.
Email us - Client portal
Log and follow your tickets, see what we are working on and who has it.
Open the portal - Remote support
When an engineer asks to see your screen, start a secure session here. You start it, so nobody sees your screen until you do.
Start a session - Chat in Microsoft Teams
Clients can message Chip, our AI assistant, in Teams to log a request without leaving their desk.
How clients reach us - Service status
Check whether Microsoft 365 or another cloud service is down before you lose an hour troubleshooting.
See live status
Questions
What people ask about shared mailboxes.
Does a shared mailbox need a licence?
Not up to 50 GB. To go to 100 GB it needs an Exchange Online Plan 2 licence, and archive or litigation hold need Plan 2 or Plan 1 with Exchange Online Archiving. Everyone who opens it needs their own Exchange Online licence.
Can we use a shared mailbox instead of a user licence?
No. A shared mailbox is for a team or role, not for one person to work from without a licence. People who access it need their own licences.
Should anyone sign in directly to a shared mailbox?
No. Each shared mailbox has an account with a system-generated password. Block sign-in for it, and give access to named people who open it from their own account.
What happens when a staff member leaves?
Their mailbox can be converted to a shared mailbox so a manager keeps access. Block sign-in on it, set an owner and an end date, and check its size and any hold needs before removing the licence.
Why do replies end up in my own Sent Items?
By default, messages sent as the shared mailbox can save to the sender's Sent Items. Turn on saving sent copies to the shared mailbox so the whole team sees the thread.
When is a shared mailbox the wrong tool?
When one person needs private help with their mail (use delegation), when you need ticket numbers and service levels (use a help desk system), or when the archive or compliance features it would need aren't licensed.
Next step
Want your shared mailboxes cleaned up?
We list every shared mailbox, block sign-in, fix access and licensing, and set an owner and review cycle for each.
Keep reading
Reviewed by Blake Bath, General Manager, on 31 October 2026. Licensing and limits from Microsoft Learn. Licences change, so check current terms. Checked 31 October 2026. Microsoft Learn, About shared mailboxes; Microsoft Learn, Exchange Online limits; Microsoft Learn, Create a shared mailbox