Outlook will no send

Hi @Robert Giltnane,

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

I can get how confusing it is to not being able to send emails and not receiving any error messages.

Messages often stay in the Outbox due to offline mode, large or blocked attachments, or Send/Receive settings that delay sending until manually triggered. Incorrect SMTP configuration, such as wrong server, port, encryption, or missing authentication, can also silently prevent delivery. Additionally, profile corruption or problematic add-ins may block the send pipeline.

Could you please check if Work Offline is currently turned on and whether the stuck emails include large attachments (over 20-25 MB)?

Here are a few steps that often help (try one after another):

1/ Bring Outlook online & send all:

• In Outlook > Send/Receive > Work Offline. If the button is selected, click it to go online > then Send/Receive > Send All.
  

2/ Free the stuck message / reduce the attachment:

• Open Outbox > drag the message to Drafts > open > delete or compress the attachment > click Send again. If Outlook says it’s transmitting, close Outlook, reopen, and retry.
• You can prefer ZIP or share via OneDrive and send a link to avoid size/type blocks.
• Reference: Troubleshoot attachment problems in Outlook for Windows

3/ Enable “Send immediately when connected”:

• File > Options > Advanced > Send and receive > check Send immediately when connected to prevent future queuing.
  

4/ Verify outgoing (SMTP) settings & run a live test:

In File > Account Settings > Account Settings > Change > More Settings:

• Outgoing Server tab > enable My outgoing server (SMTP) requires authentication.
• Advanced tab > confirm port/encryption (commonly 587 + TLS, or your provider’s values).
• Click Test Account Settings and look for all green checks.

Reference: Troubleshoot Outlook email setup

5/ Try Safe Mode (rules out add‑ins):

• Press Win+R, type outlook /safe, press Enter, then send one of the stuck emails. If it sends here, disable third‑party add‑ins.

6/ Repair the Outlook profile (and data file if needed):

• File > Account Settings > Account Settings > Email tab > select your account > Repair, then restart Outlook and test.
  
• If you suspect data‑file corruption, use SCANPST.EXE for PSTs, for Exchange/IMAP, you can delete the OST and Outlook will rebuild it on next launch.

7/ If your account is managed by an IT admin:

Ask them to confirm your mailbox isn’t listed in Restricted users (which blocks outbound mail after suspicious activity) and to review Outbound spam policies and any mail flow rules that might be rejecting outbound messages, they can also start a message trace. These checks matter when messages leave Outlook but get blocked by the service.

For reference:

• I can't send or receive messages in Outlook
• Change or update email account settings in Outlook for Windows

I hope this information is helpful. Please follow these steps and let me know if it works for you. If not, we can work together to resolve this.   

Thank you for your patience and your understanding. If you have any questions or need further assistance, please feel free to share them in the comments on this post so I can continue to support you.

I look forward to continuing the conversation.

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If Outlook is unable to send emails and they remain in the Outbox without generating error messages, consider the following potential solutions:

1. Check Send Immediately When Connected: Make sure that the "Send immediately when connected" option is enabled. If this setting is disabled, emails will stay in the Outbox until you manually perform a send/receive operation. You can enable this option by navigating to File > Options > Advanced and checking the Send and receive section.
2. Inspect for Deferred Delivery Rules: It's possible that a Deferred Delivery rule is causing the delay. To check for this, go to Rules on the Ribbon and select Manage Rules & Alerts. Look for any rules that specify a delay in sending emails, indicated by "defer delivery by" in their descriptions.
3. Disable Add-ins: Add-ins may sometimes conflict with Outlook's functionality. To see if this is the case, start Outlook in safe mode by executing Outlook.exe /safe. If the issue is resolved in safe mode, you may need to disable add-ins one at a time to find the problematic one.
4. Mailbox Size Considerations: Ensure that your mailbox is not exceeding its size limit, as this can also prevent emails from being sent.

By checking these areas, you should be able to diagnose and fix the issue preventing Outlook from sending emails.