MessageDeliveryFailedException: Could not deliver the message [len=70, Failure code: ad29 Using microsoft outlook for MAc

For Outlook for Mac, this error can align with common send/receive failures. Work through these checks in order:

1. Verify Outlook is online.
   • In Outlook, open the Outlook menu.
   • Make sure Work Offline is not checked.
2. Confirm the Mac still has Internet access.
   • Open a web browser and verify websites load.
   • If on a managed network, also confirm the network is not blocking mail traffic.
3. Check whether Microsoft cloud storage is full.
   • If cloud storage is full, Outlook for Mac may not be able to send or receive email.
4. Review the account credentials and server settings.
   • In Outlook, go to Tools > Accounts.
   • Select the affected account.
   • Verify the email address, user name, and password are correct.
   • If the mail provider requires special settings such as SSL or non-default ports, confirm those with the provider.
5. If the account is POP or IMAP, enable SMTP authentication.
   • Go to Tools > Accounts.
   • Select the account.
   • Under Outgoing server, select More Options.
   • Choose the required authentication type and enter credentials if needed.
6. If sending fails only on a specific network, check for SMTP blocking.
   • Some ISPs or networks block connections to the outgoing mail server.
   • If that is happening, use an alternative SMTP server provided by the ISP or network administrator.
   • In Tools > Accounts, select the account and update the Outgoing server value.
7. If the network uses a proxy server, confirm the proxy settings in macOS System Preferences.
8. If the server was working previously and suddenly stopped, verify the mail server is available.
   • Contact the email provider or network administrator to confirm the server is online.

If the failure happens only for certain recipients, review the delivery failure message for clues such as:

• invalid or outdated recipient address
• recipient mailbox full
• message too large
• temporary remote server timeout

For postmaster or failed-delivery messages, check the Diagnostic information for administrators section in the returned message. That section usually identifies the delivery reason.

• I can't send or receive messages with Outlook for Mac | Microsoft Support
• Sent email in Outlook.com comes back "delivery failed" | Microsoft Support
• Failed delivery messages from the postmaster at outlook.com, microsoft.com, or service.microsoft.com | Microsoft Support