Outlook not sending emails in Windows, With or Without attachments

Outlook not sending emails in Windows, With or Without attachments is when the users are unable to send emails in Windows with or without attachments. Many combinations could cause the problem, but there is one check you need to make sure you are aware of the attachment size limits offered by the Email Service you are using with Outlook. That said, in this post, we will show multiple ways to resolve the problem when Outlook is not sending emails in Windows 11/10 whether you have an attachment, or not.

Outlook not sending emails in Windows 11/10

Related Post: Stop Outlook from reopening emails after a crash

If emails aren’t working in Outlook but are on other devices, including smartphones, there are a few ways to troubleshoot the issue, To isolate the problem.

  1. Repair Outlook Profile
  2. Turn off the “Work offline” mode
  3. Increase Outlook Attachment Size
  4. Check Mailbox Settings
  5. Check Add-ins
  6. Turn of Antivirus Email Integration
  7. Zip Files before sending
  8. Blocked Files

After trying the listed solution, check to see if the problem was resolved.

1] Repair Outlook Profile

  • Open Microsoft Outlook Click on the File tab
  • Click on the “Account Settings” link under “Info” in the main menu, then select “Account Settings” from the flyout menu.
  • Select the account with the issue and click on the “Repair” button.
  • The “Repair Account” box will open. Check your settings and fields, and then click “Next.”

2] Turn off the “Work offline” mode

In Outlook, you can go through your emails without getting distracted by switching to Offline mode. In this mode, you can draft emails, but they’ll be saved in the Outbox until you disable Offline mode. To do so, open Outlook and switch to the Send/Receive section. Then, click Work Offline to disable it.

3] Increase Outlook Attachment Size

If your email service offers a maximum attachment size of 25 MB, Outlook will usually restrict any attachment that exceeds 20 MB. Luckily, you can increase the size by editing the Registry. To do this, open the Registry Editor and navigate to the following path, depending on the version of Office you’re using.

Outlook 2019 and 2016:


Outlook 2013:


Outlook 2010:


Create a new DWORD called “Maximum Attachment Size” under the “Preferences” key in the registry. If the key does not exist, right-click and create it. Double click on the new DWORD and set the value to 25600 (25.6MB) in decimal format. Start Outlook again and the attachment issue should be resolved.

4] Check Mailbox Settings

Check the mailbox settings for the email account that is causing the problem. Open Account Settings and select the email account that needs a fix. Then click on the change button. You will have options to check Mail settings, Reset Mail Settings, and so on. Use one of those options to fix the problem.

5] Disable Com Add-ins

At times, third-party plugins for Outlook, known as Com Add-ins, can cause issues, especially if they are related to attachments. However, before disabling them, make sure to open Outlook in safe mode by typing outlook.exe /safe in the run prompt. This will allow you to check if Outlook is working as expected. If it is, then you can disable the plugins one by one to see which one was causing the problem.

  • Open Outlook and select File > Options > Add-ins.
  • Manage COM Add-ins by selecting Options next to Manage.
  • If you’re having trouble with a plugin, try disabling it to see if that resolves the problem.

6] Turn off Antivirus Email Integration

If you’re using an antivirus or security solution that integrates with your email client, it might be a good idea to disable it and see if that solves the problem. If not, you may need to adjust the settings.

7] Zip Files before sending

If your file is large, you may want to zip it before attaching it to Outlook. Windows has a built-in feature to compress files. Right-click on the file or folder and select “Send To.” Then choose “Compress Folder” and it will create a zip file of that folder or file, which will be smaller in size. You should then be able to attach it and send it.

8] Blocked Files

There are a set of file types that are blocked by Outlook from being uploaded or sent as an attachment. To share those files, it’s better to rename them or use online storage instead of uploading them directly.

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