I can't Send in Outlook

Question

When I go to Send from my Outlook, I get and email back from Microsoft that says it can't send the email.

Answer 1

Who's your email service provider? Not the app you use to send email, but the actual email service itself.

The service provider's sending IP is in multiple IP blacklist. You need to contact them and make them aware. They would have to take action such as tightening outbound spam filter, or move to a different IP range, in order to improve their IP reputation score to come off blacklist.

Answer 2

Try these checks in order:

1. Confirm Outlook is online
   • In classic Outlook, look at the status bar at the bottom.
   • If it shows Disconnected, Working Offline, or Trying to connect…, go to the Send/Receive tab and select Work Offline once to switch back online.
   • Then try Send/Receive again.
2. Verify internet connection
   • Open a browser (Microsoft Edge or Google Chrome) and browse to http://www.microsoft.com or http://www.bing.com.
   • If these sites do not open, fix the network first. Outlook cannot send mail without internet access.
3. Check for large attachments
   • Open the Outbox in Outlook.
   • Open any stuck messages (start with the oldest).
   • If an email has attachments larger than about 20 MB, remove or reduce them, or replace them with a link, then send again.
4. Confirm password is up to date
   • If the account password was recently changed on the email provider’s website, update the same password in Outlook for that account.
5. Check antivirus and add-ins
   • Some antivirus tools block email sending if they detect an issue. If an antivirus message appears, follow its instructions or contact its help desk.
   • Start Outlook in safe mode to rule out add-ins: press the Windows key, type outlook.exe /safe, press Enter, then try sending again.
6. Repair Outlook or the mail profile
   • If sending still fails, run a repair of Office/Outlook.
   • If needed, repair or recreate the Outlook profile, then test sending again.

If none of these steps resolve the issue and Microsoft is sending a non-delivery report (NDR) back, check the exact error text in that returned message; it will usually indicate whether the problem is attachment size, authentication, mailbox limits, or a server-side block, and then contact support with that error text.

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References:

• I can't send or receive messages in Outlook
• My email message doesn't send
• Can't send or receive email in Outlook.com