Practical troubleshooting guide · The business scenario is illustrative, not a client case study. Administrative changes require authorised access.
A colleague can open the enquiries inbox but cannot reply from it. Another can send from the address but cannot read its messages. In Microsoft 365, opening a shared mailbox and sending from it are separate permissions. Start with the task the person needs to perform, then ask an authorised administrator to review that specific access.
Match the permission to the task
Full Access lets a delegate open and manage mailbox content; it does not grant sending rights. Send As makes a message appear to come from the shared mailbox. Send on Behalf shows the delegate acting on behalf of that mailbox. Sending permission alone does not grant reading access. If both sending permissions are assigned, Microsoft documents that Send As takes precedence. Decide whether a named delegate should be visible to the recipient before requesting a change.
Write a request your administrator can check
Use a small permission request record: mailbox address; staff account; required task; intended From identity; approver; review date. For example, a backup receptionist may need to read enquiries and reply as the enquiries address. Write both requirements down. Record any access that should remain out of scope, such as an owner’s personal mailbox. Keep passwords and verification codes out of the request. Have the responsible business owner approve the task before an administrator changes access.
Review the current delegation before adding more
In Exchange admin center, an administrator can inspect the selected mailbox under Recipients, Mailboxes and its delegation settings. Check existing grants before adding another. Microsoft documents a separate PowerShell route for Send on Behalf on shared mailboxes; do not assume every permission has the same screen control. Use the current official procedure and the administrator’s assigned permissions. Record previous values and the intended rollback. A mailbox missing from Outlook is a symptom to investigate, rather than a reason to grant every available permission.
Test opening and replying as separate outcomes
Create a harmless test message with a unique subject and no customer information. First, have the intended user open it in the shared mailbox. Next, have them select the agreed From identity and send a new test reply to an address the business controls. Record whether the reply was allowed and how its sender appeared to the recipient. If a desktop client and Outlook on the web disagree, record both results for the administrator. A successful test should demonstrate the requested task, rather than merely show a mailbox in a folder list.
Check sent copies and handover separately
Permission to send does not decide where the team will find a copy of the reply. Review shared Sent items settings as a separate task, then ask a second authorised colleague to locate the new test reply. Agree how the team marks an enquiry as being handled. This avoids treating mailbox access as an assignment system. Use the related sent-replies guide below for that distinct check. Keep the mailbox’s own sign-in blocked and let staff use their individual accounts.
Keep a compact result record
Finish the request record with the date, tester, client, opening result, sender identity, sent-copy location and unresolved issue. Name the person responsible for the next action. Review access again when cover ends or a role changes. Store the record in the business’s restricted administration notes, rather than pasting message contents into a public support request. If you ask Cyber Bounds for help, start with the mailbox symptom and intended workflow so the investigation can be scoped.
Make it actionable
Your next steps
- Agree who needs to read the mailbox and who needs to send.
- Choose the recipient-visible sender identity before changing permissions.
- Record the approver, existing grants and review date.
- Test mailbox opening, reply identity and shared sent-copy visibility separately.
- Remove temporary access through the authorised administrator when the need ends.
Official reference
Microsoft: Manage permissions for recipients in Exchange Online
Microsoft: Create a shared mailbox
Microsoft: Configure shared mailbox settings
Guide date: October 22, 2026. Product features and requirements can change. The business checklists above are practical suggestions from Cyber Bounds.
Put the next step into practice
Help with microsoft 365.
Make Outlook, Teams, and shared files work together for your business. Tell us about your situation and we’ll discuss a suitable scope and quote.
Email us about this guide