Can't send emails in Outlook

Question

I cannot send an email using Outlook. I can receive them and read them just fine, but I cannot send an email. An outgoing email gets stuck in the Outbox, and a message appears at the bottom of my screen saying "Connection to the server failed or was dropped".

Answer 1

Hi @David Clow

Thank you for posting your question in the Microsoft Q&A forum.  

To help narrow down the issue, please provide more details:  

-Are you signing in with an @outlook.com or with a @domain.com account?  

-What type of account is configured in Outlook (POP, IMAP, or Exchange)?  

-Have you tried sending messages via Outlook on the web to see if the issue persists there? 

-What version of Outlook are you currently using? 

As a temporary troubleshooting step, you may try clicking Send/Receive once to see whether Outlook reconnects and clears a message that may be stuck in the Outbox. In some cases, this can trigger a reconnection and allow the pending message to be sent.

Please know that while our initial response might not resolve the issue right away, your input is incredibly valuable. With a bit more detail, we’ll work together to find the best solution for you.  

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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  

Answer 2

Use the following checks in Outlook for Mac to resolve the “Connection to the server failed or was dropped” issue when sending mail:

1. Verify account credentials and settings

• In Outlook for Mac, go to Tools > Accounts.
• Select the affected account in the left pane.
• Confirm that:
  • Email address, user name, and password are correct.
  • Incoming and Outgoing server names match the values provided by the email service or admin.
• If the account still does not work properly, contact the email service provider or admin to confirm whether special settings are required (for example, SSL enabled and specific ports, or overriding default ports).

2. Check for firewall or network blocking SMTP

• Some ISPs or networks block connections to the outgoing mail (SMTP) server.
• If using a corporate or restricted network, contact the ISP or network administrator and ask if SMTP to the configured server/port is blocked.
• If the provider offers an alternative SMTP server or port, enter it:
  1. Tools > Accounts.
  2. Select the account.
  3. In Outgoing server, enter the alternative SMTP server name/address provided by the ISP or admin.
• If using a laptop in multiple locations, be aware that the SMTP server that works on one network may not work on another due to different firewall rules.

3. Check for required proxy settings

• If the network requires a proxy to reach external services, the mail connection can fail.
• Ask the network administrator for the correct mail proxy settings.
• Configure the proxy in macOS System Settings/Preferences as instructed in Mac OS Help, then retry sending from Outlook.

4. Confirm the mail server is online

• If this account previously worked and no settings were changed, the mail server might be temporarily unavailable.
• Contact the email provider or network administrator to verify that the mail server is online and accepting SMTP connections.

After each change, send a test message and confirm that it leaves the Outbox and appears in Sent Items.

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References:

• I can't send or receive messages with Outlook for Mac