Unable to open Outlook (Classic Outlook in Microsoft 365) from websites

Question

Unable to open Outlook (Classic Outlook in Microsoft 365) from websites

Suzanne S Barnhill 279.5K MVP Volunteer Moderator

Using the Share buttons on web pages and selecting Email, instead of opening a new message in Outlook (as expected), generates this message:

User's image

After a time, this message appears:

User's image

Microsoft 365 has just been fully updated. All apps (including Outlook) are working correctly, and I can send email from them as well as from Acrobat--just not from a browser (Chrome or Edge).

Hornblower409 15,835 Reputation points

2026-05-30T11:28:36.2866667+00:00

@Suzanne S Barnhill said

Using the Share buttons on web pages and selecting Email
from a browser (Chrome or Edge)

Not sure of the steps required to reproduce. My Chrome does not have a Share -> Email. Are you using an Extension?
Suzanne S Barnhill 279.5K Reputation points MVP Volunteer Moderator

2026-06-02T00:41:06.9933333+00:00

No. On many web pages, such as newspaper and magazine articles, there are Share options, such as this:

I can copy the link (which is what I'm currently having to do) or use the other sharing options, but the Email button generates the errors. [And I don't know why I got no notification of your comment on my post, nor why there is no AI answer.]
Hornblower409 15,835 Reputation points

2026-06-02T01:42:52.7+00:00

@Suzanne S Barnhill said

there are Share options

I found what I think you asking about on any YouTube video using the Share button.

Which is just a "mailto" link. If I click it I get a Windows prompt and choose Outlook Classic

Which opens a new mail in Classic with the link in the body

To be sure we're talking about the same thing (a mailto link) please setup one in an email.

Compose a new email. Cursor in the body of the email and Insert -> Link and fill it out with your own email. e.g.

You should now have a MailTo link in the body you can click on to test.

Does it have the same problem as when you use the Share -> Email from a web site?
Hornblower409 15,835 Reputation points

2026-06-02T01:49:07.4333333+00:00

@Suzanne S Barnhill said

why I got no notification of your comment on my post

Check your Q&A Profile -> Settings

why there is no AI answer

If you didn't "Reject" it when first posting, I don't know why you failed to get one.
Hornblower409 15,835 Reputation points

2026-06-02T03:27:35.11+00:00

why I got no notification of your comment on my post

And check your Junk/Spam folder.
Suzanne S Barnhill 279.5K Reputation points MVP Volunteer Moderator

2026-06-09T11:57:21.82+00:00

Okay, I checked, and I have pretty much everything set to Off because there's no specific setting for answers to questions I ask (I cannot be inundated by emails from threads I moderate, answer, or comment on). Moreover, there have been no answers to this question—only comments. It would be interesting to see what would happen if you would post your advice as an answer rather than a comment.
Suzanne S Barnhill 279.5K Reputation points MVP Volunteer Moderator

2026-06-09T12:03:08.18+00:00

I tried the mailto link as suggested (I had noticed yesterday that I couldn't click on a mailto link in another email—got the same response), and I get the same two dialogs. I do NOT get a prompt to choose an app. I checked my default settings, and Outlook (classic) is already selected as the default app.

Answer accepted by question author

0 additional answers

Your answer

Hornblower409 15,835 Reputation points

2026-05-30T11:28:36.2866667+00:00

@Suzanne S Barnhill said

Using the Share buttons on web pages and selecting Email
from a browser (Chrome or Edge)

Not sure of the steps required to reproduce. My Chrome does not have a Share -> Email. Are you using an Extension?
Suzanne S Barnhill 279.5K Reputation points MVP Volunteer Moderator

2026-06-02T00:41:06.9933333+00:00

No. On many web pages, such as newspaper and magazine articles, there are Share options, such as this:

I can copy the link (which is what I'm currently having to do) or use the other sharing options, but the Email button generates the errors. [And I don't know why I got no notification of your comment on my post, nor why there is no AI answer.]
Hornblower409 15,835 Reputation points

2026-06-02T01:42:52.7+00:00

@Suzanne S Barnhill said

there are Share options

I found what I think you asking about on any YouTube video using the Share button.

Which is just a "mailto" link. If I click it I get a Windows prompt and choose Outlook Classic

Which opens a new mail in Classic with the link in the body

To be sure we're talking about the same thing (a mailto link) please setup one in an email.

Compose a new email. Cursor in the body of the email and Insert -> Link and fill it out with your own email. e.g.

You should now have a MailTo link in the body you can click on to test.

Does it have the same problem as when you use the Share -> Email from a web site?
Hornblower409 15,835 Reputation points

2026-06-02T01:49:07.4333333+00:00

@Suzanne S Barnhill said

why I got no notification of your comment on my post

Check your Q&A Profile -> Settings

why there is no AI answer

If you didn't "Reject" it when first posting, I don't know why you failed to get one.
Hornblower409 15,835 Reputation points

2026-06-02T03:27:35.11+00:00

why I got no notification of your comment on my post

And check your Junk/Spam folder.
Suzanne S Barnhill 279.5K Reputation points MVP Volunteer Moderator

2026-06-09T11:57:21.82+00:00

Okay, I checked, and I have pretty much everything set to Off because there's no specific setting for answers to questions I ask (I cannot be inundated by emails from threads I moderate, answer, or comment on). Moreover, there have been no answers to this question—only comments. It would be interesting to see what would happen if you would post your advice as an answer rather than a comment.
Suzanne S Barnhill 279.5K Reputation points MVP Volunteer Moderator

2026-06-09T12:03:08.18+00:00

I tried the mailto link as suggested (I had noticed yesterday that I couldn't click on a mailto link in another email—got the same response), and I get the same two dialogs. I do NOT get a prompt to choose an app. I checked my default settings, and Outlook (classic) is already selected as the default app.

Answer 1

Hornblower409 15,835

@Suzanne S Barnhill said

what would happen if you would post your advice as an answer rather than a comment.

This is an Answer and not a Comment.

I tried the mailto link as suggested ... get the same two dialogs [Updating Microsoft 365 and Outlook App Error 0xC0000143] I do NOT get a prompt to choose an app. I checked my default settings, and Outlook (classic) is already selected as the default app.

1 -- One more test to be sure that the problem is opening Outlook with a MailTo command line (this is what happens behind the scenes when you click on a MailTo link)

Open a Windows CMD or Terminal window and execute:
START mailto:"******@mail.com?cc=******@mail.com&subject=MySubject&body=MyBody"

The forum censor will have replaced the user part of the emails with asterisks

2 -- Try an Outlook Repair
https://support.microsoft.com/en-us/office/repair-an-office-application-7821d4b6-7c1d-4205-aa0e-a6b40c5bb88b

3 -- Test with Outlook in Safe Mode (disables all Add-Ins)
https://support.microsoft.com/en-us/office/open-outlook-in-safe-mode-f394c2ee-b2af-e97a-64ee-35cd24414811

4 -- Test with a new Profile
https://support.microsoft.com/en-us/office/create-an-outlook-profile-f544c1ba-3352-4b3b-be0b-8d42a540459d

Suzanne S Barnhill 279.5K Reputation points MVP Volunteer Moderator

2026-06-10T00:43:49.9666667+00:00

Well, I didn't get a notification, but #1 seems to have shaken something loose (mailto links appear to be working now).

I had already repaired Outlook (as part of a Microsoft 365 online repair), and that hadn't helped. I didn't get as far as Safe Mode.

We'll see if this has fixed it. If so, I'll come back and accept your answer. Thank you for your patience! This problem has definitely tried mine!
Suzanne S Barnhill 279.5K Reputation points MVP Volunteer Moderator

2026-06-10T11:28:07.7166667+00:00

The fix seems to be holding this morning. Thanks again!