Outlook sending problem

Question

I am getting undeliverable sending emails. I sent the email in question many times in past with no problems.

Answer 1

I am using Microsoft Office Professional Plus 2024, Outlook.

Error: You do not have the permission to send the message on behalf of the specified user.

I test by sending an email to my other email addresses

I have sent emails many times

 

Answer 2

Hello,

Is this regarding your outlook.com email address?
Have you tried sending it directly from the web www.outlook.com and see if it goes out from there?

Also, can you please share the bounce email's complete content? It contains important diagnostic data that helps shed some light of the root cause. Feel free to redact personal information when you share.

Answer 3

Undeliverable messages usually mean the receiving mail system rejected or could not accept the message, even if the same email worked in the past. The non‑delivery report (NDR) normally includes a specific error text that points to the cause.

Based on common Outlook.com/consumer scenarios, check the following in the bounce message and act accordingly:

1. Check the exact error text in the NDR
   Look for phrases like:
   • "Mailbox not found", "Invalid mailbox", or "User unknown": The address no longer exists or changed.
     • Verify there are no typos in the recipient address.
     • If possible, contact the recipient another way to confirm their current email address.
   • "Mailbox full" or "Quota exceeded": The recipient’s mailbox is out of space.
     • If there is another way to reach the recipient, let them know their mailbox is full so they can free space and then you can resend.
   • "Mailbox unavailable": Often similar to “Mailbox not found,” but can also be a temporary issue on the recipient side.
     • Wait a short time and try sending again.
     • Re‑check the address for typos and confirm with the recipient if possible.
   • "Message too large": The message (often due to attachments) exceeds the recipient server’s size limit.
     • Remove or reduce attachments.
     • Upload large files to OneDrive and send a sharing link instead.
   • "Host unknown" or "Domain lookup failed": The domain part of the address (after the @) does not exist or cannot be resolved.
     • Confirm the domain is spelled correctly and that the recipient is still using that domain.
   • Errors mentioning "blocked" or "listed in" (e.g., spamcop, spamhaus, dynablock, blackhole): The recipient’s server is treating the sending server/account as spam.
     • Contact the recipient’s email provider support and request that the account or sending domain be unblocked.
   • "Can't connect to remote server", "Connection timed out", "No adequate servers", "Out of memory", "Resources temporarily unavailable": Usually temporary issues on the recipient’s side.
     • If the NDR says the recipient’s provider will keep trying, no action is needed.
     • Otherwise, wait a while and resend.
2. If the address is correct but still getting NDRs
   • If using an Outlook.com address and the NDR confirms the recipient address is valid, follow the guidance in Sender Support in Outlook.com (linked from the Outlook.com sending issues article) so Microsoft can investigate deliverability problems.
3. If the message has attachments
   • Ensure the total size is under 25 MB if sending from Outlook.com.
   • If larger, upload files to OneDrive and send a link instead.
4. If this is a new or rarely used Outlook.com account
   • A low sending quota may temporarily limit sending until normal reputation is established. In that case, review the Outlook.com sending limits guidance referenced in the Outlook.com sending issues article.

If the exact error text from the undeliverable report is available, match it against the categories above and apply the corresponding fix, then resend the message.

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References:

• Sent email in Outlook.com comes back "delivery failed"
• Can't send or receive email in Outlook.com