NEW Outlook .EML - X-Unsent: 1 - Sending not working multiple times

Question

NEW Outlook .EML - X-Unsent: 1 - Sending not working multiple times

Spielezar AG 20

We use .eml files as templates. The first row contains the following:

X-Unsent: 1

This way we can open a template, edit it to our needs and send it. It all looks charming, but when clicking on "Send" the email is just not sent. No error at all. This email closes as always.

I believe the system thinks "this email was already sent". I shouldn't send it again. But in fact that's exactly what we want.

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Phoebe-N 10,685 Microsoft External Staff Moderator

Hi @Spielezar AG

Welcome to Q&A Community!

Thank you for reaching out. I’ve tested sending EML files with the X-Unsent:1 header in the new Outlook, and it appears to function normally on my end. Therefore, to investigate further, I’d like to gather some additional details from you:

Are you having a Personal (@hotmail.com, @live.com, @gmail.com) or Work/School account (@yourcompany.contoso)?
 Could you confirm that the email was sent to the correct recipient? If not, you should receive a Non-Delivery Report (NDR).
Have you checked if the email appears in your Sent Items folder?
Are there any rules configured that might affect sent items? If possible, please share a screenshot of your rules for review.

To check mail flow rules, kindly go to Outlook > Settings > Mail > Rules.

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Can you try sending the same email using Classic Outlook and let me know if the issue persists?

In the meantime, kindly ask your admin to run a message trace to verify where the email is and confirm whether it was sent successfully.

For detailed instructions, please read this article Message trace in the new EAC in Exchange Online | Microsoft Learn

Once I have the above information, I'll be able to narrow down the cause and assist you further. Thank you for your cooperation, and please let me know if you have any questions.

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

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Spielezar AG 20 Reputation points

2025-09-22T14:31:42.3+00:00
We use our company email @company.ch

The email is sent, the first time. Aftewards it is no more sent.

It doesn't go into sent folder. After clicking on "Send" the email just closes as it would have been sent, but nothing had happened actually.

There are no rules as this is not even supported for external domains.

In classic outlook this was always working. But there we used .oft files extension.

We don't use exchange server. Maybe the section "for business" is not correct. Didn't know what to select as we use a @company.ch email.
Phoebe-N 10,685 Reputation points Microsoft External Staff Moderator

2025-09-23T12:28:44.7833333+00:00
Hi @Spielezar AG

Thank you for your prompt updates.

To create .eml file in New Outlook, please confirm that you clicked "Save as EML" after creating the draft email. And after creating the .eml file, you can only send once. As I tested, the same issue happened to me. As there is currently no official article related to this issue, I have done some research and here is a workaround that I tried, and it worked on my part.

According to what I have researched, while an .eml file is created in that way, it goes with its unique message ID. To view it, right-click the file > Edit in Notepad and you will see your file details.

X-Unsent: 1 is a special email header used in .eml files to indicate that the message is an unsent draft while the Message-ID in an .eml file is a unique identifier for that email message. It’s part of the email headers and looks something like this: Message-ID<******@mailserver.domain.com>

This means, if you want to send the same .eml file various times, you need to remove its message ID. You can copy the ID and create a new tab in Notepad, then paste it there. In this way, the .eml file can be sent multiple times.

As this workaround works on my side, please try following the steps and let me know if it helps resolve your issue.

Please note that as a forum moderator, I don't have permission to any direct products updates or changes.

If you would like Microsoft to investigate this further or consider adding full support for this feature in New Outlook, I'd recommend you submit feedback directly to the Outlook team.

In New Outlook, click Help (question mark icon) in the top-right corner.

Select Feedback > Report a Problem or Suggest a Feature.

Provide details about your scenario (using .eml templates with X-Unsent: 1 and the need for consistent draft behavior).

This feedback goes directly to the product team and helps prioritize improvements in future updates.

Thank you so much for your patience and cooperation.
Spielezar AG 20 Reputation points

2025-09-23T13:12:58.43+00:00

Thanks a lot! Removing the message-id is working for me too. I have made a report to the official Outlook team :)
Phoebe-N 10,685 Reputation points Microsoft External Staff Moderator

2025-09-23T13:34:42.59+00:00

Hi @Spielezar AG

Thank you so much for your good news. I'm thrilled to hear that the given steps help resolve your issue.

Thank you for your cooperation and kind words. I appreciate it.