Shared mailboxes let a team monitor and reply from a common address such as info@, support@, or sales@ without each person needing a separate paid license. Replies are sent from the shared address, and everyone with access sees the same conversation history. Here is how to set one up correctly.
Step 1: Create the shared mailbox
Sign in to the Microsoft 365 admin center, then go to Teams & groups → Shared mailboxes → Add a shared mailbox. Give it a clear display name and the address you want, for example [email protected]. A shared mailbox under 50 GB does not consume a license.
Step 2: Assign members
After the mailbox is created, edit its membership and add the users who need access. Each member gets two permissions automatically: Read and manage (Full Access) and Send as. Full Access lets them open the mailbox; Send as lets them reply as the shared address.
Step 3: Decide between Send As and Send on Behalf
"Send as" makes the message appear to come directly from support@. "Send on behalf" shows "Jane Doe on behalf of support" in the From line. For customer-facing mailboxes, Send as is almost always what you want, since it presents a unified brand voice.
Step 4: Access the mailbox
Members can open the shared mailbox in Outlook on the web via their profile picture → Open another mailbox, or add it as an additional account in the desktop client. Because permissions propagate through Microsoft 365, allow up to 60 minutes before access reliably appears.
Step 5: Enable copies of sent items
By default, replies sent from a shared mailbox are saved in the sender's personal Sent Items, not the shared one. To keep the team in sync, run a short PowerShell command to enable MessageCopyForSentAsEnabled on the mailbox so every sent reply lands in the shared Sent folder.
Shared mailboxes are one of the highest-value, lowest-cost features in Microsoft 365. Set them up once, document who has access, and review membership when people join or leave.
Korur Security Team
Korur Security Team