Shared Mailboxes, Distribution Lists, and Microsoft 365 Groups, What's the Difference and Which Should You Use?

The question Hamilton365 gets asked more than almost any other when working with small and medium businesses on their Microsoft 365 environments: "What's the difference between a shared mailbox and a group?" Here's a clear breakdown.

Distribution Lists

A collection of email addresses under a single alias. Delivers a copy of each email to every address in the list. One-way broadcast only, no shared inbox, no collaboration. Use for: all-staff announcements, team newsletters, broadcast communications.

Shared Mailboxes

A mailbox multiple people can access and send from, without a dedicated licence (up to 50GB). Replies come from the mailbox address. Use for: bookings@, support@, accounts@, info@, functional addresses where someone needs to respond on behalf of the address. Critical: assign clear ownership to every shared mailbox.

Microsoft 365 Groups

A collaboration unit including a shared mailbox, SharePoint document library, Planner board, and optional Teams channel. Every Team in Microsoft Teams has a Microsoft 365 Group behind it. Use for: ongoing team collaboration with files, conversations, and shared email.

Decision Framework

Just need to send to a group? → Distribution List. Need multiple people monitoring a shared inbox? → Shared Mailbox. Need a team to collaborate? → Microsoft 365 Group. Need shared inbox AND collaboration? → M365 Group plus potentially a separate shared mailbox.