Shared mailbox vs user mailbox

Overview

Exchange Online has two ways for several people to work in one mailbox. A shared mailbox is built for team email and has no sign-in of its own. A user mailbox belongs to one person, always needs an Exchange Online license, and can be shared with others through delegated permissions. Knowing the difference helps you set up Microsoft Exchange correctly.

Key differences

Feature	Exchange shared mailbox	User mailbox shared with others
Ownership	No individual owner. Multiple users can access it.	Owned by one user.
Access	Through permissions assigned to multiple users. Users don't share sign-in details.	Through permissions the owner delegates to others.
Sign-in	No sign-in of its own. Users access it with their own accounts and the right permissions (Full Access, Send As, or Send on Behalf).	Tied to the individual user's sign-in.
Licensing	No license if the mailbox is under 50 GB. Over 50 GB, it needs an Exchange Online Plan 2 license.	Always needs an Exchange Online license.
Email sending	Email is sent from the shared mailbox's address. Users need Send As or Send on Behalf permission.	Email is sent from the user's own address, unless Send As or Send on Behalf is set up.
Designed for	Team-based email, such as customer service or shared inboxes.	Personal use, shared for collaboration when needed.

When to use each

Shared mailbox

Customer service or team addresses, such as support@example.com or info@example.com, and general inquiry mailboxes that several team members use.

User mailbox shared with others

A personal mailbox whose owner needs to delegate access to an assistant or team member, such as an executive assistant who manages another user's mailbox.

Licensing

• Shared mailboxes under 50 GB don’t need a license.
• Shared mailboxes over 50 GB need an Exchange Online Plan 2 license.
• Every user who accesses a shared mailbox must have an Exchange Online license.
• User mailboxes always need an Exchange Online license.

Additional resources

• Microsoft Learn: About shared mailboxes
• Microsoft Q&A: Difference between shared mailbox and user mailbox
• Microsoft Tech Community: Shared mailbox use, Send As
• Emazzanti: Shared mailbox vs regular mailbox in Microsoft Exchange
• Alif Consulting: User mailbox vs shared mailbox

What’s next

• Send As vs Send on Behalf: the two sending permissions, and how they differ.
• Setting up signatures for shared inboxes: each signature uses the sender’s signature block.
• Setting up shared inboxes for Stamping customers: the same setup for Stamping customers.