Outlook in Macbook doesn't send internal emails

Use this Outlook for Mac troubleshooting path for messages that fail to send and get saved to Drafts:

1. Verify Outlook is online.
   • In Outlook, open the Outlook menu.
   • Make sure Work Offline is not checked.
2. Check the account credentials and account settings.
   • Go to Tools > Accounts.
   • Select the affected account in the left pane.
   • Confirm the email address, user name, and password are correct.
   • If the mail provider requires special settings such as SSL or a non-default port, confirm those settings with the mail provider.
3. Turn on SMTP authentication if this is a POP or IMAP account.
   • Go to Tools > Accounts.
   • Select the account.
   • Under Outgoing server, select More Options.
   • Choose the required authentication type and enter the credentials.
   • This is relevant when Outlook can receive mail but cannot send.
4. Check whether the network or ISP is blocking the outgoing mail server.
   • If the Mac is on a restricted network, firewall rules can block SMTP.
   • If available, get an alternative SMTP server from the ISP or network administrator.
   • Enter it in Tools > Accounts > select account > Outgoing server.
   • This is especially relevant if the issue happens only on that Mac or only on one network.
5. Check whether a proxy is required on that network.
   • Some networks require a mail proxy server to reach the mail server.
   • Configure the proxy in macOS System Preferences if the network administrator says one is required.
6. Confirm the mail server is available.
   • If the account worked before, the mail server may be temporarily unavailable.
   • Check with the email provider or network administrator.
7. If the failed message has large attachments, reduce the message size.
   • Outlook for Mac can keep oversized messages in Drafts instead of sending them.
   • Open the message in Drafts, remove some attachments, and send again.
   • If the message is no longer needed, delete it from Drafts and then permanently delete it from Deleted Items to stop repeated attachment errors.
8. If this only fails when sending as a group, shared list, security group, or mail-enabled public folder, send from a single mailbox instead.
   • Outlook for Mac cannot send from a distribution list, security group, or mail-enabled Public Folder.
   • In that case, use a single account or a Microsoft 365 Group instead.

If the issue is specifically with @shaw.ca or rogers domain accounts in Outlook for Mac, there is a known issue under investigation where users may be unable to send or receive mail.

If none of the steps above resolves it, use Help > Contact Support in Outlook for Mac.

• I can't send or receive messages with Outlook for Mac | Microsoft Support
• Errors when sending emails from security groups, distribution lists, or mail-enabled Public Folders in Outlook for Mac
• My email message doesn't send | Microsoft Support
• Outlook for Mac fails to send email with SMTP error '-3253' or 'Connection to the server failed or dropped' | Microsoft Support