Legacy Outlook for Mac is now deleting threads when emails are replied or forwarded

Question

It appears that this topic (not being able to have your email in Legacy Outlook for Mac retain the thread of an email conversation) has been ongoing issue since mid-May of 2026.

Now that I've updated to Mac Outlook Version 16.110, I'm having the same issue.

The recommend (at an identically-named question thread here) by a Microsoft External Staff Moderator to someone mid-May was to wipe out this current version of Mac Outlook and revert to an earlier version. This is a very temporary solution, soon enough there will be critical security updates that we shouldn't be opting out of.

Can any Microsoft Moderator please weigh in on whether Microsoft has any intention of restoring this functionality to the Legacy version of MS Outlook?

9Sorry, but the current non-Legacy version of Outlook for Mac was a notable step back from the cleaner simpler Legacy version, it manages space very poorly, shows far too little info at-a-glance, has other issues – I'm not planning on using that if it can at all be helped).

Thanks so much -

Answer 1

Hi @Mark K and @Admin Panel
Currently, in similar cases you could switch to the Current Channel (Preview) and update Outlook to version 16.110.1 to help avoid this issue. To do this, go to Help > Check for Updates > Advanced, select Current Channel (Preview), then close the pane and click the update button to install version 16.110.1. After the update completes, restart Outlook and try again.

This sign indicates an official fix will be rolled out in near future.
I hope this helps.

Answer 2

Hi @Mark K

Thank you for reaching out. 

First, I’d like to clarify that this is a user‑to‑user support forum. Moderators participating here do not have access to backend systems, nor can we directly intervene in Microsoft product functionality. Our role is limited to providing technical guidance and sharing best‑practice recommendations based on reported issues, requests, and scenarios. 

I truly understand your concern regarding this issue, and I sincerely appreciate you taking the time to share your experience. Currently, Microsoft has confirmed this as a known issue in Outlook for Mac build 16.110. It specifically affects the Legacy Outlook experience, where the original email content is not included when replying to or forwarding messages. The Outlook team is actively working on a fix. 

You can refer via: Replying to or forwarding an email does not include the original message in the email body in legac… 

Regarding the new Outlook software for Mac, I also agree that it may not yet fully meet your expectations in terms of interface, usability, and completeness of features. As the product is still evolving, there may be limitations or differences that impact your workflow. Your feedback in this area is extremely valuable, and I would strongly encourage you to continue sharing your thoughts and expectations. To help improve the overall user experience and influence future updates, I recommend sharing your feedback through the Feedback Portal and sharing the link here. This dedicated platform allows users to provide direct insight into how specific changes impact their workflows and to suggest ideas for product improvements. If other users are experiencing similar challenges or would benefit from this feature in New Outlook for Mac, their votes can help increase visibility and priority for the product team.  

Once again, I truly appreciate your patience and understanding.

If you have any additional concerns, feel free to comment below. I would be more than happy to assist. 

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Answer 3

re: the AI answer.
"Conversation grouping" is another matter.

This is the much simpler topic of including the content of an existing email in the email response one sends.
There is a radio button to turn this on and off in the settings (Settings/Composing/Attribution of original message), which whether turned on or off, it no longer works in the latest update.

Answer 4

Legacy Outlook for Mac conversation-thread behavior was recently affected by a bug introduced in version 16.96, where emails stopped grouping correctly into conversations even when “conversation” and “show in groups” were enabled. This issue has been explicitly acknowledged and fixed by the Outlook for Mac team.

According to the documented fix, the problem with conversation grouping in Legacy Outlook for Mac was resolved in build 16.96.25042021 (released April 22, 2025). After installing that build (or any later build that includes the fix), users may need to clear the cache on the affected folder to restore correct conversation grouping. Guidance is provided in the “Clear the cache in Outlook for Mac” article referenced from the fix.

There is no indication in the provided documentation that Microsoft plans to remove conversation-threading functionality from Legacy Outlook for Mac; instead, the documented position is that the bug was fixed and conversation grouping should work again once the fixed build (or newer) is installed and the folder cache is cleared.

However, it is also documented that:

• Legacy Outlook for Mac is being phased out in favor of the new Outlook for Mac.
• Legacy Outlook for Mac relies on Exchange Web Services (EWS) for Exchange Online, and EWS in Exchange Online will be retired on October 1, 2026.
• Starting October 2026, Legacy Outlook for Mac will stop working against Exchange Online mailboxes (though it will continue to work with Exchange On-Premises mailboxes).

Because of this retirement, long-term investment in Legacy Outlook for Mac is limited, and Microsoft strongly recommends switching to the new Outlook for Mac to ensure ongoing support, security, and reliability. If conversation-thread issues persist in Legacy Outlook despite being on a fixed build, the supported path is to:

1. Ensure Outlook for Mac is updated to a build at or beyond 16.96.25042021.
2. Clear the cache on the folder where conversation grouping is incorrect, following the “Clear the cache in Outlook for Mac” guidance.
3. If the issue remains, use in-app support (Help > Contact Support) or, for work/school accounts, contact the organization’s help desk so they can open a support ticket.
4. Plan a transition from Legacy Outlook for Mac to the new Outlook for Mac before EWS retirement and the end of Legacy Outlook’s ability to connect to Exchange Online.

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References:

• Legacy Outlook for Mac emails are not grouped in Conversation threads as expected for Exchange OnPremise/Office 365 and Google accounts
• Fixes or workarounds for recent issues in Outlook for Mac
• End of support for legacy Outlook for Mac