Outlook Failure

Since the same message sends successfully from Network Solutions Webmail, the mailbox and recipient path are likely working, and the Outlook client is the area to check.

Try these Outlook checks in order:

1. Verify Outlook is set to send immediately
   • In Outlook, go to File > Options > Advanced.
   • Under Send and receive, make sure Send immediately when connected is enabled.
   • If this is off, messages can leave the Outbox only after a manual Send/Receive.
2. Check for a Deferred Delivery rule
   • Go to Rules on the ribbon > Manage Rules & Alerts.
   • Review each rule on the Email Rules tab.
   • Look for a rule description that includes defer delivery by # minutes.
   • If found, open that rule and clear the deferred delivery action.
3. Check whether Outlook is repeatedly trying to send a hidden stuck item
   • A stuck read receipt can cause Outlook to keep sending even when the Outbox appears empty.
   • This can show up as Outlook reporting that it is sending messages although no visible messages are queued.
4. If Outlook shows it is offline or messages stay unsent until manual Send/Receive
   • One documented cause is Outlook running with a specific registry value: LoadTransportProviders=1 under HKEY_CURRENT_USER\Software\Microsoft\Office\<x.0>\Outlook\Preferences.
   • Deleting that value is the documented fix.
   • Warning: editing the registry incorrectly can cause serious problems.
5. If the issue is only with certain recipients and Outlook shows SMTP errors such as 550/5.x.x
   • That points to the recipient mail server rejecting the message rather than Outlook failing to send.
   • Test by sending a simple message with no attachment to a different recipient.
6. If Outlook shows sync errors or undeliverable reports mentioning 80040611 or Invalid named property
   • That is a different known issue tied to mailbox/OST corruption from excessive named properties.
   • The documented workaround is to pause Digital Guardian if present, then request a mailbox move through Microsoft 365 Admin support and recreate the OST.

Based on the symptoms described, the most likely Outlook-side checks are Send immediately when connected and Deferred Delivery rules first. If Outlook is showing send progress, errors, or NDR text, that exact message is the key to narrowing it down further.

• Outlook email stuck
• Email messages remain in the Outbox because of Deferred Delivery rule
• Outlook keeps trying to send a nonexistent message while Outbox folder shows zero messages
• Outlook email stuck
• Outlook sync issues cause emails to be stuck in the Outbox and undeliverable mail items
• Outlook will not send emails - Microsoft Q&A