Office 365 apps insist on using Outlook Classic to share documents to email

Question

Office 365 apps insist on using Outlook Classic to share documents to email

Mark Fenton 5

Windows desktop environment

Latest Microsoft 365 apps (as of today)

set default app settings to New Outlook wherever possible
Verify Explorer.exe calls new Outlook to send documents as attachment.
From within New Outlook, can attach and send files/links etc normaily

To reproduce issue:

Launch Word and create new document
Select to share doc to email as attachment
Word calls Outlook Classic to send the email.

The same behavior occurs in the other M365 apps (Excel, PowerPoint, etc)

Extremely annoying.

Charles Kenyon 166.1K Reputation points Volunteer Moderator

2026-01-06T03:28:05.68+00:00

You are correct. That is what happens. It is by design.

Outlook Classic is a much more flexible and powerful email client.
Beining, Nic 0 Reputation points

2026-01-12T19:52:39.2266667+00:00

So frustrating. Especially if you forget to launch Outlook Classic after so that the file actually sends.

Answer recommended by moderator

2 additional answers

Your answer

Charles Kenyon 166.1K Reputation points Volunteer Moderator

2026-01-06T03:28:05.68+00:00

You are correct. That is what happens. It is by design.

Outlook Classic is a much more flexible and powerful email client.
Beining, Nic 0 Reputation points

2026-01-12T19:52:39.2266667+00:00

So frustrating. Especially if you forget to launch Outlook Classic after so that the file actually sends.

Answer 1

Suzanne S Barnhill 277K MVP Volunteer Moderator

New Outlook is not MAPI-compliant, so it is not possible to use it for mail merges from Word or for emailing Word documents as attachments directly. At least Word is opening New Outlook and allowing you to attach files, which is an improvement over just not doing anything, but using Classic Outlook as your default mail client exclusively would avoid any such annoyances.

0 comments

Answer 2

Dear @Mark Fenton,

Thank you for posting your question in the Microsoft Q&A forum.

Based on your description, when you use Word, Excel, or PowerPoint to share a document via email > Send as Attachment, the apps still open Outlook Classic instead of New Outlook, even though New Outlook is set as the default

Unfortunately, New Outlook does not fully support MAPI, Office apps automatically fall back to Outlook Classic to complete the Share‑to‑Email action.

This means that even if New Outlook is set as the default mail app in Windows or File Explorer, Office desktop applications will still open Outlook Classic whenever they need those older APIs.

Microsoft is still in a transition phase, many integrations (mail merge, PST write support, advanced features, full offline support, and some automation APIs) are still missing in the New Outlook and will be added gradually.

Besides that, here is workarounds you can refer to:

Attach the File Manually Inside New Outlook

Instead of using “Share > Email,” you can:

Open New Outlook directly
Click New Mail
Use Attach File or drag‑and‑drop the document into the new message

As Outlook continues to evolve, new features and settings may be introduced in future updates. I encourage you to submit feedback through the Microsoft Ideas Community at Ideas · Community so that the product team can review user preferences.

As a forum moderator, I do not have the authority to influence Microsoft’s updates, features, or design decisions as user. I always try my best to provide helpful information and possible workarounds to support you with the issue you’re experiencing.

I hope information above meet your expectation, if you have any other questions, please feel free to reach out.

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Darren-Ng 9,180 Reputation points Microsoft External Staff Moderator

2026-01-07T05:15:20.11+00:00

Dear @Mark Fenton,

Just checking in to see if the above information was helpful. If you have any further updates on this issue, please feel free to post back. If you think my reply is helpful to you, please remember to mark it as an answer. Warm thanks.
Doug Robbins - MVP - Office Apps and Services 322.8K Reputation points MVP Volunteer Moderator

2026-01-07T05:47:14.47+00:00

Per advice from the Outlook Product Team, MAPI compliance will not be added to the New Outlook.

Answer 3

Inger Christensen 55

We are experiencing that the mails sent this way is being sent very delayed, is this reported to Microsoft?

It is one thing is that it is using classic outlook, but it is critical if the mail is not sent right away.

Stefan Blom 337.8K Reputation points MVP Volunteer Moderator

2026-02-04T10:14:56.81+00:00

@Inger Christensen,

When you "share" via e-mail, it appears the process is slower. Also, Outlook must be open at the time you choose the share option.

If you have further questions regarding this, I recommend that you start your own thread. Use the Ask a question link at the top of the page. Good luck.
Edwards, Greg [MB] 6 Reputation points

2026-03-27T14:32:45.01+00:00

We are experiencing the same pain. Since New Outlook doesn't support MAPI, the Office app helpfully launches a Classic Outlook message - but since Classic Outlook is only open for that moment, that message doesn't send for days - so we get countless helpdesk tickets about email not working. There are forums that mention this going back for over 3 years... Microsoft needs to (preferably) come up with a way for New Outlook to support this, or at least give us the option to disable the feature in Office programs....
Charles Kenyon 166.1K Reputation points Volunteer Moderator

2026-03-27T15:33:19.8366667+00:00

@Edwards, Greg [MB]

I doubt it will change.
Why not simply use Outlook classic rather that the "new" version?

This is a user-to-user support forum.

Microsoft is not hearing about your problems from what you post here. You are discussing a problem with your fellow users here. We can give good advice about how to work with Word as it is and give suggestions for making it work properly.

Designers and their supervisors do see feedback. (You will almost certainly not get a direct response to that feedback but they do see it.)

Here is more about that:

https://answers.microsoft.com/en-us/msoffice/forum/all/giving-feedback-on-microsoft-word-or-other/8df81a9b-84aa-46ef-bf88-24fb7fec96ba

I suggest using the public feedback portal so other users can see your feedback, comment and vote. If you want, you can post the URL of your feedback with your question here to lead others with the same problem to your feedback. Be the “squeaky wheel” that gets fixed!

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Office 365 apps insist on using Outlook Classic to share documents to email

2 additional answers

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