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1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesBefore replacing Microsoft 365 shared mailboxes, groups, or distribution lists with Proton, identify what each object actually does. Proton Groups are designed for email distribution; Proton’s documented Microsoft 365 Easy Switch flow migrates user accounts, not shared mailboxes; and a Microsoft 365 Group may support calendars and other collaboration resources that a mailing list does not replace. The safe approach is to inventory each workflow, choose a replacement by function, and pilot it before changing mail delivery.
First, identify which Microsoft 365 object you have
“Group” can mean several different things in Microsoft 365. A shared mailbox, a standard distribution list, a dynamic distribution group, and a Microsoft 365 Group have different jobs and permissions. Use Microsoft’s group comparison and group management documentation to confirm the object type in your tenant.
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| Microsoft 365 object | What it does | What to check before replacing it | Proton consideration |
|---|---|---|---|
| Shared mailbox | Gives multiple people access to one mailbox and can include a collaborative calendar. Authorized users may send as the mailbox or on its behalf. | Who has Full Access, Send As, and Send on Behalf; how replies and sent copies are handled; calendar use; mailbox history and retention; address-list visibility. | Proton’s documented Microsoft 365 Easy Switch user-account flow excludes shared mailboxes. Plan their data and shared-inbox workflow separately. |
| Standard distribution list | Distributes messages to a defined membership list. | Who may send to it; whether senders or members are external; list owners, aliases, and membership; whether the list also has an informal collaborative role. | Proton Groups are the closest documented fit when the need is email forwarding to group members. |
| Dynamic distribution group | Calculates recipients from rules when messages are sent rather than relying only on a fixed membership list. | The recipient rules, their data source, how often they change, and whether the resulting recipient set can be reproduced elsewhere. | Do not assume a Proton Group will reproduce rule-based recipient selection. Confirm how membership would be maintained. |
| Microsoft 365 Group | Provides a group mailbox and shared calendar, with collaboration resources such as Planner and SharePoint depending on subscription and setup. | Which connected resources are in use, who owns them, and what happens to files, tasks, calendar entries, and conversation history. | A Proton Group is documented as an email-forwarding feature; that does not establish equivalence for Microsoft collaboration resources. |
For shared mailboxes, the permission names matter: Full Access lets a delegate open and manage mailbox contents, while Send As and Send on Behalf govern distinct ways of sending. Microsoft says sign-in is blocked by default for a new shared mailbox. Its shared mailbox setup guide also notes that hiding a mailbox from address lists can affect Send As or Send on Behalf behavior in Outlook desktop. Check the tenant’s actual settings and client behavior, not just the mailbox name. See also Microsoft’s shared mailbox overview.
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Can I migrate Microsoft 365 shared mailboxes and distribution lists to Proton?
Proton documents an Easy Switch process for migrating Microsoft 365 user accounts, but its guide says: “Microsoft 365 shared mailboxes are not currently supported and will not appear in this list.” That is a limitation of the documented Easy Switch flow; it does not establish that no manual or separately supported migration method exists. If a shared mailbox is essential, ask Proton for written confirmation of the available path before setting a cutover date.
The business migration guide requires the operator to have administrator access in both Proton and Microsoft 365, and it supports cloud-hosted Microsoft 365 accounts rather than on-premises accounts. It lets an administrator select emails, contacts, and calendars and migrate user accounts in batches. The documented process includes a final MX-record change, and Proton warns that unused activation links stop working after migration is finalized. Confirm the current operational steps with Proton’s Microsoft 365 business migration guide when planning the move.
Does Proton have shared mailboxes?
The cited Proton documentation does not establish a direct shared-mailbox equivalent with the same concurrent inbox handling and delegation behavior as Microsoft 365. Proton organization users have their own inboxes. Administrators can access non-private users, but access to a private user’s messages requires that user to accept access; neither arrangement should be treated as automatically equivalent to shared-mailbox delegation. Review Proton’s guidance on user roles and private users.
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For each shared mailbox, write down how the replacement will handle incoming mail, team visibility, sending from the shared address, sent copies, historical messages, and any audit or retention needs. Test those actions with real users and clients. If shared-inbox behavior is a hard requirement, get confirmation that the proposed approach supports the specific behavior your team relies on.
How do Proton Groups compare to Microsoft 365 Groups?
Proton describes Groups as forwarding email sent to a group address to its members, a function also known as a mailing list or distribution list. Administrators can set who may send to the group address: Everyone, Group members, or No one, with per-member overrides. This makes Proton Groups a plausible fit for email-only lists, not evidence of a like-for-like replacement for a Microsoft 365 Group’s wider workspace.
External participants affect encryption: Proton states, “If you add a non-Proton Mail email address to the group, end-to-end encryption for messages going to the group address will be turned off.” Include that trade-off in the decision if the list needs non-Proton members. Proton’s Groups documentation lists Mail Professional (now deprecated), Proton Workspace, and Visionary with a custom domain as eligible plans; verify current eligibility and feature availability on Proton’s Groups page.
Microsoft’s overview describes Microsoft 365 Groups as a broader collaboration object. It currently lists support for more than 1,000 members, with up to 1,000 members able to access group conversations concurrently, and a 50 GB group mailbox. These are Microsoft-published product limits, not assurances about migration or Proton capacity. Check the Microsoft 365 Groups overview alongside your tenant’s actual connected services.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Build a migration plan around the work each object performs
- Inventory the current configuration. Record each object’s primary address and aliases, owners, members, sender restrictions, external senders or members, dynamic membership rules, data-history needs, and any calendar, file, task, or automation dependencies.
- Classify the job. Mark each object as a shared operational inbox, a simple email list, a rule-based distribution group, or a collaboration workspace. Do not classify by display name alone.
- Separate shared mailboxes into their own workstream. Specify how their messages, permissions, replies, sent copies, history, and audit needs will work after migration. The documented Easy Switch path does not include them.
- Rebuild email-only lists as a pilot. For a representative Proton Group, test allowed senders, membership changes, external participants, invitation acceptance, and the resulting encryption behavior.
- Map Microsoft 365 Group dependencies. Decide for each connected resource whether it can be retired, replaced with a separate service, or must remain. Do not treat matching email addresses as proof that the workspace has been replaced.
- Test before changing MX records. Pilot a simple distribution list, a list involving external senders or members, a shared mailbox, and a collaboration-heavy Microsoft 365 Group. Verify permissions, client behavior, delivery, and data history with the people who use them.
Microsoft-to-Microsoft conversion procedures are not Proton migration instructions. Microsoft’s distribution-list upgrade applies only to eligible cloud-managed, simple, non-nested lists; Microsoft separately documents converting a distribution list to a shared mailbox by freeing the address, creating a mailbox, adding members, and granting permissions. Microsoft also states that a shared mailbox cannot be migrated to a Microsoft 365 Group. Those procedures describe Microsoft services, not a route into Proton. See the distribution-list upgrade guidance and conversion guidance.
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