Can’t @mention Someone in a Word Comment? Fix the Right Failure

If Word will not let you @mention a colleague in a comment, first identify which part failed:

1. their name never appears or will not resolve;
2. the mention is created, but no notification arrives; or
3. the notification arrives, but the person cannot open the document.

Those are different faults. Clearing Office caches, deleting Normal.dotm, removing a sensitivity label or changing a guest account is not a sensible first response.

The two-minute diagnosis

Test	Result	Next check
Is the file saved in SharePoint or OneDrive for work or school?	No	Move or save the collaboration copy to an approved cloud location
Are you signed in to Microsoft 365 in Word?	No	Sign in with the account that has access to the file
Does the person appear when you type @ plus their name or alias?	No	Check the exact address, directory visibility and tenant/guest identity
Does the mention appear in the comment, but no email arrives?	Yes	Check whether the file is checked out or hidden by draft-item security
Does the email arrive, but the link gives access denied?	Yes	Grant the recipient access to the document or site as appropriate
Does it work in Word for the web but not desktop Word?	Yes	Update and re-authenticate the desktop app; do not alter tenant settings yet
Does it fail for every user in web and desktop apps?	Yes	Capture evidence and raise a Microsoft 365 support case

Microsoft’s @mention support page states that the work-or-school document should be saved in a SharePoint library or OneDrive for work or school. On Windows, it also says the user needs to be signed in to Outlook on the PC for the feature.

1. Prove the basic Word @mention path

Use a simple test document so that old permissions and document state do not muddy the result.

1. Create a new Word document in an approved SharePoint document library or OneDrive for work or school.
2. Confirm that both people can open it in Word for the web.
3. Add a new comment.
4. Type @ followed by the person’s exact name or email alias.
5. Select the resolved person from the list and post the comment.
6. Confirm separately that the comment exists, that a notification is received, and that its link opens the file.

Microsoft says that if the selected person does not already have permission to open the document, Word can ask you to provide it. Treat that prompt as a permission decision: share only if the file’s owner and your organization’s policy allow it.

This test gives you a baseline. If it works, the tenant-wide mention service is not your first suspect; compare the failing document’s location, state, permissions and audience.

2. If the person’s name will not resolve

Try the exact email alias rather than relying on a partial display name. Then test another known user.

Microsoft documents one specific cause for an unresolved person: the mailbox is hidden from the global address list. That troubleshooting article applies to Word, Excel, PowerPoint and Outlook.

An Exchange administrator can check the mailbox deliberately:

$User = Get-Mailbox -Identity alex@contoso.com
$User.HiddenFromAddressListsEnabled

If the value is True, that explains why the person does not resolve. It does not automatically mean the administrator should expose them. A mailbox may be hidden intentionally—for example, because it is a service, shared or sensitive account. Confirm the directory policy and the account’s purpose before changing anything.

Where visibility should be restored, Microsoft documents:

Set-Mailbox -Identity alex@contoso.com -HiddenFromAddressListsEnabled $false

Do not promise that a fixed number of minutes will make every client update. Retest the new cloud document in Word for the web first, then the supported desktop clients.

For an external collaborator, first confirm that you are using the identity that actually has access to the SharePoint or OneDrive file. Microsoft’s external-collaboration overview explains that document sharing uses guest accounts and that guests can access only resources specifically shared with them. Do not delete and recreate a guest merely because a name search failed; that can break existing access and audit continuity.

3. If the mention is created but no email arrives

This is not a people-picker problem.

Microsoft’s SharePoint troubleshooting article documents two relevant conditions when an @mention exists but the notification is not sent:

• the file is checked out; or
• the file is in Draft state and the library’s Draft Item Security setting does not let every reader see drafts.

Check the document library:

1. Select the file and inspect whether it is checked out.
2. If appropriate, check it in and test with a new comment.
3. If content approval or minor versions are enabled, inspect Library settings > Versioning settings > Draft Item Security.
4. Do not weaken draft security simply to make a notification work. If readers should not see the draft, publish or approve the document through the normal process instead.
5. Ask the recipient to check mailbox rules, quarantine and junk only after the document-state check.

Microsoft says an @mention notification includes a link to the comment. Notification delivery and file permission remain separate: receiving the email does not prove that the link will open.

4. If the person receives the mention but cannot open the file

Open Manage access for the document and inspect direct access, group access and sharing links. Microsoft’s Manage access guidance shows how to see who a file is shared with, stop sharing or change permissions.

Then verify:

• the recipient is signed in as the same identity that was granted access;
• the link is still valid;
• the site’s external-sharing policy permits the recipient;
• the document is checked in and visible to that permission level;
• a sensitivity label or Conditional Access policy is denying access by design.

Do not remove a sensitivity label as a general troubleshooting step. If a protection policy blocks access, ask the document owner or compliance administrator whether the recipient should be allowed. The correct fix may be a different document, audience or sharing route—not weaker protection.

5. If Word for the web works but desktop Word does not

That comparison points to the desktop client, account or device rather than the document’s core SharePoint state.

Use this order:

1. Confirm Word and Outlook are signed in with the intended work or school account.
2. Install the organization’s supported Microsoft 365 Apps updates.
3. Close and reopen the document from SharePoint or OneDrive, not an old local copy.
4. Sign out and back in only if your support policy permits it and you understand the effect on other Office apps.
5. Retest the same comment in Word for the web and desktop Word.

Do not begin by deleting Office caches or the user’s Word template. Those actions can discard useful state and preferences without fixing a document, permission or directory problem.

6. Capture useful evidence for the administrator

For an unresolved incident, provide:

• the document’s SharePoint or OneDrive location;
• Word for the web versus desktop result;
• whether the name resolves;
• whether the comment is created;
• whether the email arrives;
• whether the recipient can open the link;
• internal user versus guest identity;
• whether the file is checked out, a draft or approved;
• one affected and one working account;
• UTC time and a screenshot with confidential content removed.

If the failure affects everyone across fresh cloud documents in both web and desktop apps, raise a Microsoft 365 support request. A tenant-wide failure needs service-side diagnostics, not more destructive local resets.

Frequently asked questions

Does the Word document have to be in SharePoint or OneDrive?

For Microsoft 365 work-or-school @mentions, Microsoft’s current instructions start with a document saved in a SharePoint library or OneDrive for work or school. A local file is not a reliable collaboration baseline.

Why can I mention some colleagues but not one person?

Check the exact alias and account first. Microsoft documents hidden global-address-list visibility as one cause of an unresolved user, but an administrator should confirm that state before changing it.

Why did the comment post without sending an email?

Microsoft documents checked-out files and draft-item security as causes for missing @mention notifications in SharePoint files. Check those states before changing mail or directory settings.

Does an @mention automatically give someone access to the document?

Word can prompt you to share when the person lacks permission, but access is still a separate, governed decision. Verify the recipient’s actual permission and sign-in identity.

Should I clear the Office cache or delete Normal.dotm?

Not as a first step. First isolate cloud location, sign-in, name resolution, notification and file access. Only perform a client reset when evidence points to that client and you have a reversible support procedure.

For practical Microsoft 365 fixes that keep identity, sharing and document state separate, join the Microsoft 365 Productivity Workers Space. Bring the failure stage and a redacted test result.