Email delivery failed

Question

when i sent email to another person then my email dose not sent and the outlook postmaster send me feedback like "Delivery failed". why this is doing contineuosly? i need solution immedietly.

Answer 1

Hello. Could you please open one of the "Delivery failed" emails you received from Outlook Postmaster and tell us exactly what the error message says?

Please copy the full error message, including any error codes, such as 550 or 5.7.1, or share a screenshot with any personal information hidden.

Also, does this happen when emailing everyone, or only certain recipients?

Answer 2

Because delivery fails to every recipient, send one new, attachment-free message from Outlook.com; if it also fails, use the detailed code in the postmaster report to identify a sender-account restriction or other specific cause.

Test from Outlook.com

1. Sign in directly at Outlook.com.
2. Create a new message rather than forwarding or resending the failed one.
3. Send it to one known-valid address.
4. Remove:
   • All attachments
   • Your email signature
   • Links or copied formatted content
5. Type the recipient’s complete address manually instead of selecting an Auto-Complete suggestion.

Outlook.com cannot send an attachment larger than 25 MB, and signatures can sometimes affect sending. If necessary, upload a large file to OneDrive and send its link instead.^1^

Find the actual error code

Open the delivery-failure message and expand or scroll to Diagnostic information for administrators. Copy the status line after removing all email addresses. It may contain a code such as:

• 550 5.1.8
• 5.1.1
• 5.7.1
• AS(42004)
• “mailbox full,” “message too large,” “blocked,” or “Spamhaus”

The short text “Please try resending” does not identify the cause; the diagnostic section normally contains the delivery reason.^2^

Apply only the branch matching that code:

• 550 5.1.8, “bad outbound sender,” or AS(42004): This can indicate a sending restriction. Check Sent Items for messages you did not send and secure the account if suspicious activity exists. For a personal Outlook.com account, contact Outlook.com support. If this is actually a Microsoft 365 work or school account, the organization’s email administrator must investigate and unblock it.^3^
• “Blocked,” “listed in,” Spamhaus, SpamCop, or another blocklist: The recipient’s filtering provider may be rejecting the sender. Contact that provider and request review or removal of the block. Do not treat every 5.7.x response as an Outlook.com account restriction.[^4^](https://support.microsoft.com/outlook/sent-email-in-outlook-com-comes-back-delivery-failed#undeliverable "Sent email in Outlook.com comes back "delivery failed" | Microsoft Support")
• Mailbox full, unknown user, or invalid mailbox: The recipient must free storage or provide a current address. This is unlikely when every unrelated recipient fails.
• Connection timed out, resources temporarily unavailable, or message expired: Wait briefly and resend. These normally indicate a temporary receiving-server problem.[^4^](https://support.microsoft.com/outlook/sent-email-in-outlook-com-comes-back-delivery-failed#undeliverable "Sent email in Outlook.com comes back "delivery failed" | Microsoft Support")

Check the Outlook.com account

Check whether Microsoft cloud storage is full; a full account cannot send or receive email. An account can also be temporarily blocked after unusual sign-in activity. Newly created Outlook.com accounts may initially have a lower sending quota.^5^

If storage is available and the minimal test still fails for every valid address:

1. Open Outlook.com.
2. Select Help on the menu bar.
3. Enter cannot send email to any recipient.
4. Complete the self-help flow.
5. Scroll to Still need help? and select Yes to contact Outlook.com support.^5^

Microsoft also directs users who have confirmed that a recipient address is correct but still receive a non-delivery report to Sender Support in Outlook.com.^1^

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References

1. Can't send or receive email in Outlook.com | Microsoft Support
2. Failed delivery messages from the postmaster at outlook.com, microsoft.com, or service.microsoft.com | Microsoft Support
3. How to fix the mail deliverability issue on my exchange account? - Microsoft Q&A
4. Sent email in Outlook.com comes back "delivery failed" | Microsoft Support
5. Can't send or receive email in Outlook.com | Microsoft Support