email keeps coming back undelivered

Question

My emails aren’t sending and it keeps coming back with the below technical detail

Technical details

MessageDeliveryFailedException: Could not deliver the message [len=70, data=000000009C29EBAC46E7EF479E9424184B46F70D07008D92241585117F4581F96C03A302387200000000010F00008D92241585117F4581F96C03A302387200005A232E340000] sent at 6/5/2025 11:01:24 PM.
Failure code: 700

What’s does it mean and how do I fix it?

Answer 1

Same issues, with my gmail account, from yesterday. It's a disaster to be obliged to use the new outlook, is the the 10 times i had big problems and i cannot back to old version, on new laptop. A nightmare!

Please do not ask if private or business, fixed the problem and let leave and work the people payng for use your tools.

Answer 2

Hi Bruno Constante Goedert,

Thanks for reaching out and sharing all the details. I'm glad to help you!

We’ve looked into the issue you’re experiencing with New Outlook, where emails stay stuck in Drafts and eventually fail to send with the error:

MessageDeliveryFailedException

Failure code: 700

This seems to be affecting all recipients.

This specific error code isn’t currently documented by Microsoft, but based on similar cases, it looks like the problem is tied to how New Outlook handles sending emails with IMAP accounts, especially with third-party providers like Hostinger.

It seems that New Outlook may delay sending or handle drafts differently, which can lead to failures like the one you're seeing.

Could you try switching back to Classic Outlook (the old version) and see if the issue still happens there?

• Open Outlook
• Look for the toggle in the top-right that says “Try the New Outlook”
• Switch it off
• Restart the app when prompted

The Classic version tends to be much more stable when working with IMAP/SMTP accounts like the one you’re using from Hostinger.

If switching back solves the problem (which it often does), then we’ll know for sure it’s a New Outlook compatibility issue. And from there, we can either stick with the classic version or explore other options.

Let us know how it goes. Looking forward to your response!

Sincerely,

Jeanie-H - MSFT | Microsoft Community Support Specialist.

Answer 3

Hello Microsoft Support and Community,

I'm also encountering an issue with the New Outlook application (begining 06.04.2025) where emails fail to send and remain in the Drafts folder. After approximately one day, the email is sent but returns the following error:

Technical Details: MessageDeliveryFailedException: Could not deliver the message [len=70, data=000000008F168D91F019524EB5E24C0EF712E64707005B5BA0331591DB4CB1AB190463720B7700000000010F00005B5BA0331591DB4CB1AB190463720B7700001C1BF9A80000] sent at 6/6/2025 12:32:02 AM. Failure code: 700

Environment:

• Application: New Outlook Desktop
• Account Type: IMAP
• Operating System: Windows 11
• Email Provider: Hostinger

Additional Notes:

• The issue occurs consistently for all recipients, regardless of the domain.
• The email content is short (as indicated by len=70 in the error).
• No recent changes to account settings, passwords, or DNS records.

Could you please assist in identifying the cause of the MessageDeliveryFailedException with failure code 700? Are there specific logs or diagnostic steps I can provide to help troubleshoot? Any insights into whether this is related to New Outlook’s IMAP handling or server-side issues would be appreciated.

Thank you for your support!

Answer 4

Hi Jeanie-H and Microsoft Support,

Thank you for your prompt response and suggestion to switch to Classic Outlook.

I resolved the issue by deleting my IMAP account from New Outlook and re-adding it. After reconfiguring the account with the same IMAP/SMTP settings provided by my email provider, emails now send successfully without getting stuck in Drafts or triggering the MessageDeliveryFailedException (failure code 700).
Thank you again for your support.

Answer 5

Hi Dan Simpson, 

Thank you for reaching out to us. I'm glad to help you! 

To better assist you and identify the root cause, I’d like to kindly ask for a few additional details: 

Could you please confirm whether your Outlook account is a personal or business account? 

Just to clarify, did this issue occur specifically on the Outlook app for iOS? 

If possible, could you try to reproduce the issue on: Outlook Web, Outlook Desktop, both Classic and the New Outlook experience? 

Could you let us know what type of account you’re using? (POP, IMAP, or Exchange) 

When you have a moment, please check if there are any Inbox Rules that might be affecting your ability to send emails. 

Are all outgoing emails being returned as undelivered, or is this happening only with certain emails? 

If specific, are the recipients internal (within your organization) or external? 

Are there any common patterns, such as file attachments, message formatting, or subject lines, between the affected emails? 

Once we have this information, we’ll be in a much better position to investigate further and work toward a resolution. Thank you again for your patience and cooperation, I truly appreciate it. Looking forward to your response! 

Sincerely, 
Jeanie-H - MSFT | Microsoft Community Support Specialist.