Reply All not working

Question

One of our staff is trying to reply all from a shared inbox, however when she clicks reply all it acts like she is just replying in that it only brings up one email address.

What could be causing this? Other people using the same shared inbox are not having the same issue.
Moved from Outlook | Windows | New Outlook for Windows | For home

Answer 1

I hope you understand my patience; since you are using a business account, I will continue to assist you in resolving this issue.
Dear @Brendan Thomas,

I understand the frustration when a "Reply All" function behaves like a simple "Reply," especially when collaborating in a shared inbox. Since this issue is isolated to only one staff member, it is likely a local client configuration or a corrupted profile rather than a permission issue with the shared mailbox itself.

Here are the most common causes and the steps I recommend resolving this:

Step 1: Check Outlook for Web (OWA)

First, have the user log in to Outlook via a web browser (outlook.office.com) and try "Reply All" from the shared inbox there.

• If it works on the web: The issue is specifically with her local Outlook desktop application.
• If it does not work on the web: Please verify if her "Send As" or "Send on Behalf" permissions were recently modified.

Step 2: Disable "Simplify Ribbon" or Outlook "New" Experience

Sometimes, the "Simplified Ribbon" in the classic Outlook or the "New Outlook" toggle can change how action buttons behave. Ask the user to:

• Ensure they are clicking the actual Reply All button and not a combined action button that defaults to "Reply."
• Try using the keyboard shortcut Ctrl + Shift + R to see if it correctly populates all recipients.

Step 3: Clear the Outlook Cache (RoamCache)

A corrupted local cache can cause UI glitches.

1. Close Outlook.
2. Navigate to %localappdata%\Microsoft\Outlook\RoamCache.
3. Delete the files in this folder (this will not delete emails, only temporary UI/autocomplete data).
4. Restart Outlook.

Please refer to this document: How to clear cache in Outlook: new app and classic version

This link is shared by community members for your convenience. It points to a third-party site that is not managed or verified by Microsoft. I can’t guarantee the quality, safety, or suitability of any content or software found there. Please review carefully and make sure you understand any potential risks before using it. 
Step 4: Recreate the Outlook Profile

Since other users are not affected, the user’s Outlook profile may be corrupted.

• Go to Control Panel > Mail > Show Profiles.
• Create a New Profile, add her account, and let the shared inbox automap again. This is often the most effective "clean slate" solution for specific client errors.

Step 5: Check "Conversations" View Settings

In some cases, if "Show as Conversations" is enabled, Outlook may struggle to identify all recipients across a complex thread if the local index is out of sync. Try toggling this setting off under the View tab.

For further technical details on managing shared mailboxes, you can refer to the Microsoft official documentation on Shared Mailboxes.

I hope this helps your staff member get back to normal operations quickly.

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Answer 2

Hi Brendan Thomas

Please confirm the following:

• Is this a work/school Microsoft 365 shared mailbox (organization-managed), or a personal Outlook.com account?
• For the affected user, does the issue also occur in Outlook on the web when accessing the same shared mailbox, or only in new Outlook for Windows?

How is the shared mailbox added for the affected user:

• Appears under Shared with me, or
• Added as a full account (shows under Your accounts in Settings)?

I would love to hear from you soon. Have a lovely day!

Answer 3

The described behavior is not covered by the documented issues in the provided context. The available articles address different reply/reply-all problems (buttons not working in Outlook for Mac, reply-all failures in Microsoft 365 Groups in Outlook on the web/new Outlook, and server-side Exchange bugs), but none match a single user in a shared mailbox having Reply All act like Reply.

Because no cause or fix for this specific scenario is documented in the context, no supported explanation can be given from these sources.

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References:

• Selecting Reply, Reply All, and Forward buttons is not working as expected
• Can't use Reply All in email messages in Microsoft 365 groups
• Outlook Web App replies to the wrong email address when an email has more than 12 recipients in Exchange Server 2013
• Default from delegate's address in shared mailboxes in Exchange Server 2013
• my outlook email is not delivered - Microsoft Q&A
• Not receiving emails in a timely manner. - Microsoft Q&A
• Microsoft app launcher (waffle icon) isn't showing apps in Outlook - Microsoft Q&A
• Stopped receiving emails on my account. - Microsoft Q&A
• Outlook Freezing and Not Responding and Not saving changes when ending the task - Microsoft Q&A