Outlook will not send emails to recipients

Question

Outlook will not send emails to recipients. When I send emails they never arrive to the recipients. What is wrong with outlook that sent emails never deliver?

Answer 1

Hi @Walton Johnston,

Welcome to the Microsoft Q&A forum.

I would like to provide you with the following information:

To resolve this issue, you can try the methods below:

1/ Update the account password If you have recently changed your password, please update the password for your account in Outlook Classic:

Select File > Account Settings > Update Password

2/ Clear the Outbox Emails stuck in the Outbox may block other emails from being sent. Please follow these steps:

Open Outbox > right-click the stuck email > select Move to Drafts

3/ Check whether Outlook Classic is in Online or Offline mode Select Send/Receive and check the connection status.

4/ Perform an Online Repair for Outlook

• Step 1: Press Windows + I
• Step 2: Select Apps > Installed apps > Microsoft 365
• Step 3: Select the … icon > Modify > Online Repair

5/ Create a new Outlook profile

• Step 1: Open Control Panel
• Step 2: Select Mail (Microsoft Outlook)
• Step 3: Select Show Profiles > Add > create a new profile
• Step 4: Return to Show Profiles > select Always use this profile

6/ Check whether add-ins are causing the issue

• Step 1: Open Outlook in Safe Mode by pressing Windows + R, then enter: outlook.exe /safe
• Step 2: Open Outlook and check whether the issue still occurs
• Step 3: If the issue no longer occurs, an Outlook add-in may be the cause
• Step 4: Open Outlook normally
• Step 5: Select File > Options > Add-ins > Go
• Step 6: Uncheck all add-ins, then enable them one by one to identify the problematic add-in

You can refer to the following document: Outlook Will Not Send Emails? 24 Proven Fixes [2026 Guide]

This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.

At the same time, please help me check whether the issue also occurs when you use New Outlook or Outlook on the web.

In addition, could you please let me know the current status of Outlook Classic (the status shown on the status bar at the bottom-right corner of the application)?

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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Answer 2

Several common issues can cause Outlook for Windows (classic) to send messages that never arrive at recipients. Use these checks and fixes in order:

1. Verify if messages are actually leaving Outlook

• Check Sent Items: If the message is not in Sent Items, it may be stuck in Outbox or blocked by an add‑in/antivirus.
• If messages appear in Sent Items but recipients do not get them, continue with the steps below.

2. Check for Non‑Delivery Reports (NDRs) or postmaster messages

• Look in Inbox and Junk Email for messages from ******@outlook.com, postmaster@microsoft.com, or service.microsoft.com.
• Open the postmaster/NDR message and scroll to the “Diagnostic information for administrators” section.
• The diagnostic text usually explains why delivery failed (for example, invalid address, mailbox full, attachment too large, blocked as spam).
• Correct the issue indicated (fix the address, reduce attachment size, ask the recipient to clear space or unblock the sender) and resend.

3. Check for known Outlook send bugs and update Outlook

• Some builds of Outlook for Microsoft 365 have had bugs where messages fail to send and generate NDRs with specific error codes.
• Example: NDRs with Error [0x80040305-0x00000000-0x00000000] when sending from Outlook Desktop, or Error [0x80004005-0x00000000-0x00000000] when replying/forwarding due to a bad autocomplete entry.
• These issues are marked STATUS: FIXED in newer builds. Install the latest Office updates:
  • In Outlook: File → Office Account → Update Options → Update Now.
• If the NDR mentions a bad autocomplete entry (failure enum(7)), delete the recipient from the autocomplete list and retype the address before resending.

4. Confirm account password and connection

• If the account password was changed on the email provider’s website, it must also be updated in classic Outlook. Otherwise, send/receive can silently fail.
• Update the password in the account settings or recreate the account if needed.

5. Check antivirus and add‑ins

• Some antivirus products scan email and can block sending when they detect an issue.
• If antivirus email scanning is enabled, temporarily disable just the email‑scanning feature or consult the antivirus help desk.
• Start Outlook in Safe Mode to rule out add‑ins:
  • Press the Windows key, type outlook.exe /safe, then press Enter.
  • If email sends successfully in Safe Mode, create a new Outlook profile and disable problematic add‑ins.

6. Repair Outlook and/or the Outlook profile

• If send/receive is generally unreliable or inconsistent, repair the Outlook installation:
  • Use the Office repair process described in Repair an Office application.
• If the issue appears tied to one profile, repair or recreate the Outlook profile:
  • Follow Fix your Outlook email connection by repairing your profile / Create an Outlook profile.

7. If using Outlook.com or Microsoft 365 mailboxes, check service‑side causes

• For Outlook.com or Microsoft 365 accounts configured in classic Outlook, delivery failures may be due to:
  • Invalid recipient address.
  • Recipient mailbox full.
  • Recipient server issues.
  • Spam/blacklist filters blocking the message.
• The NDR text will usually state one of these reasons. Adjust the recipient list, correct addresses, or ask the recipient’s admin/provider to unblock the sender/domain.

If, after these steps, messages are in Sent Items but no NDRs are received and recipients still never get them, review any postmaster messages carefully and work with the email administrator to inspect server‑side logs and anti‑spam policies.

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References:

• Emails sent using Outlook Desktop results in Non-Delivery Report [0x80040305-0x00000000-0x00000000]
• Can't send or receive messages in Outlook
• Outlook replies or forwards cause non-delivery error “Your message did not reach some or all of the intended recipients”
• Failed delivery messages from the postmaster at outlook.com, microsoft.com, or service.microsoft.com
• Sent email in Outlook.com comes back "delivery failed"