Outlook in Macbook doesn't send internal emails

Román Balboa Catalán 20 Reputation points
2026-11-11T19:18:56.7133333+00:00

I have an user with a Macbook that's trying to send an email to a coworker but he can't do it.

When selecting 'Send' a small red alert inform that there was an error, followed by an option to 'Open" and that option just takes us back to the failed mail. These failed mails are saved as Drafts.

I tried to delete the autocomplete of those internal emails yet again, it failed.

I would appreciate some feedback on how to solve this problem.

Thanks.

Outlook | MacOS | New Outlook for Mac | For business
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  1. Ryan-N 16,950 Reputation points Microsoft External Staff Moderator
    2026-11-11T19:28:03.7833333+00:00

    Hi Román,

    Welcome to the Microsoft Q&A forum.

    To better assist you, please provide the following information:

    1/ Can the user send emails through Outlook on the web on the same macOS device?

    2/ Please also perform a Message Trace to gather more information about the email delivery process and help identify why the email was not sent successfully. After running the Message Trace, the report may provide additional information about the status of the email and the reason it could not be sent.

    You can follow the steps in the documentation below to run a Message Trace:

    Message trace in the new EAC in Exchange Online | Microsoft Learn

    Once completed, please share the following information with me:

    • The error code or reason specified in the Message Trace report.
    • If you cannot find the email in the Message Trace results, please let me know as well.

    I look forward to your response.

    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. 

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  2. AI answer

    2026-11-11T19:19:15.66+00:00

    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.

    AI-generated content may be incorrect. Read our transparency notes for more information.

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