Not able to send email from desktop Outlook - failure code ad29

Lenka Milaberská 0

Hello there, I have an issue with sending emails from desktop Outlook app as shown below (failure code ad29). I already tried solution recommended here https://learn.microsoft.com/en-us/answers/questions/5986707/how-to-fix-the-problem?page=1&orderby=Helpful&comment=answer-12932633&translated=false#newest-answer-comment but is not helping in my case. I even tried to delete my mail account from otlook and add it again, no difference. Sending mail from webmail works, from outlook on mobile as well. What should I do next? Thank you

MessageDeliveryFailedException: Could not deliver the message [len=70, 
Failure code: ad29

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6 answers

Emma1-N 12,285 Reputation points Microsoft External Staff Moderator

2026-09-04T07:17:08.4666667+00:00
Welcome Lenka Milaberská,

Thank you for posting. Since you can send emails successfully from Outlook on the web and on your mobile device, the mailbox itself appears to be working, and the issue is likely related to the Outlook desktop client. The ad29 error shown in similar cases is associated with a message failing to be delivered from Outlook.

To help narrow this down, could you please confirm:
- Are you using classic Outlook or new Outlook for Windows?
- Does the error occur with all emails or only specific messages?
- Do those messages contain attachments?
In the meantime, please try this quick test:
- Open Outlook and create a brand-new email with only a short subject and a few words in the body.
- Send it to your own email address.
- If it fails, check whether the message remains in Outbox, Drafts, or disappears completely.
Please let me know the Outlook version and the result of the test email, and I can suggest the next troubleshooting step.
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Lenka Milaberská 0 Reputation points

2026-09-04T08:08:50.8933333+00:00

Hi @Emma1-N

I think I use the new Outlook, but please see version details below:

App version: 1.2026.818.100

Client version: 20260821009.10

WebView2 Version: 152.0.4191.53 (Stable)

The error occurs with all emails, not depending if there is an attachment or not, the same for emails with Test in subject and in body of the email sent to my account. After hitting Send button, the email moves to Drafts folder and few hours later I receive an email shown below.

Emma1-N 12,285 Reputation points Microsoft External Staff Moderator

2026-09-05T07:39:43.3566667+00:00

Hello Lenka Milaberská,

Remove and re-add the account using a fresh sign-in:

Remove the account from new Outlook.

Close Outlook completely.

Reopen Outlook and add the account again.

When prompted, sign in through the Microsoft authentication window and complete any verification steps.

Lenka Milaberská 0 Reputation points

2026-09-06T17:21:52.55+00:00

Hello @Emma1-N

as written in my post above, I've already tried this. No result, the issue occured in the same way even after removal and adding the account again.

I also want to mention that from the same Outlook app, sending emails from other accounts is working without any issues. But, at the same time, I can send emails from the problematic account without issue from my mobile Outlook app, and the setting of account is the same on both devices. Also, previously the email sending was working without any issues, the problem exists for past three weeks.

Lenka

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Emma1-N 12,285 Reputation points Microsoft External Staff Moderator

2026-09-08T04:12:15.3933333+00:00

Hello Lenka Milaberská,

Please follow the steps outlined above. Once completed, let me know whether the issue has been resolved, and I will continue assisting you.
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Not able to send email from desktop Outlook - failure code ad29

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