Emails stuck in Outbox of Mail app on Windows 10

You have multiple email accounts set up in the Mail app on Windows 10 but you notice that when you try to send an email from one of the email accounts, the email gets stuck in Outbox, whereas, you’re able to send the same email using other email accounts via the same Mail app. In some cases though, it appears all the other email accounts are affected. This post will help you with solutions to resolve this anomaly.

Emails stuck in Outbox of Mail app

If you’re faced with this issue, you can try our recommended solutions below in no particular order and see if that helps to resolve the issue.

Use a different email client
Run Windows Store Apps Troubleshooter
Reset Mail app
Re-register Mail app with PowerShell
Allow Mail and Calendar app through Windows Firewall
Update Mail and Calendar app
Update Windows 10
Configure device to allow access to email
Adjust the ports used in the Mail app
Delete email account and re-add account

Let’s take a look at the description of the process involved concerning each of the listed solutions.

1] Use a different email client

You can try sending the email using another email client for Windows 10.

2] Run Microsoft Store Apps Troubleshooter

This solution requires you to run the inbuilt Microsoft Store App Troubleshooter and see if the problem is resolved.

3] Reset Mail app

To reset the Mail app on Windows 10, do the following:

Press the Windows key + I to open Settings.
Tap or click the Apps category.
Under the Apps & features, scroll to locate or search for the Mail and Calendar app.
Expand the Mail and Calendar app.
Open Advanced options.
Scroll down and click on the Reset button.
Open the Mail app, sign in with your credentials and send the emails.

If the issue persists, try the next solution.

4] Re-register Mail app with PowerShell

To re-register the Mail app using PowerShell in Windows 10, do the following:

Press Windows key + X to open the Power User Menu.
Tap A on the keyboard to launch PowerShell in admin/elevated mode.
In the PowerShell console, type or copy and paste in the command below and hit Enter:

Get-AppxPackage Microsoft.windowscommunicationsapps | Remove-AppxPackage

After the command executes, restart your PC.

On boot, fire up the Mail app and try sending emails and see if the issue is resolved. If not, proceed with the next solution.

5] Allow Mail and Calendar app through Windows Firewall

To allow the Mail and Calendar app through the Windows Firewall on Windows 10, do the following:

Press Windows key on the keyboard and type allow apps.
Select Allow an app through Windows Firewall from the search result.
Click on the Change settings button. You’ll need administrative permission to access settings.
Scroll down and confirm that Mail and Calendar can freely communicate through Firewall. Make sure both Public and Private networks are enabled.
Confirm changes if needed.
Click OK.

You can now exit the Allowed applications applet.

Additionally, if you have third-party security software that includes an active firewall, make sure to allow the Mail and Calendar app through.

Now, check if mails still get stuck in the Outbox when you send an email. If so, continue with the next solution.

6] Update Mail and Calendar app

This solution entails that you update the Mail and Calendar app on Microsoft Store. Here’s how:

Open Microsoft Store.
Click on your Profile on the top right of Microsoft Store.
Select Download and Updates
Click Check for updates to see if any update is available for Mail & Calendar app.

If the issue persists, try the next solution.

7] Update Windows 10

Windows updates on Windows 10 cover everything. Besides the common security patches and various fixes for the OS, updates can also be available for all built-in applications. So you need to manually check for Windows update and install the new bits if any and see if the Mail app issue is resolved. Otherwise, try the next solution.

8] Configure the device to allow access to the email

Do the following:

Open Settings.
Tap or click the Privacy category.
Scroll down on the left pane to locate and select Email.
Under the Allow access to email on this device section, click Change and confirm that the option is toggled On.
Under the Choose which apps can access your email section, make sure that the Mail and Calendar app is toggled On.

Exit the Settings app when done and see if the issue is resolved. If not, try the next solution.

9] Adjust the ports used in the Mail app

Do the following:

Open Mail app.
Right-click the problematic account.
Select Account settings from the menu.
From the Account settings dialog, select Change mailbox sync settings.
Scroll down to the bottom of the dialog and select Advanced mailbox settings to display the incoming and outgoing email servers.

Incoming email server: You can get this information from your ISP or administrator. Usually, an incoming mail server address is in the format of mail.contoso.com or imap.google.com. For many email accounts, you can find this information in the POP and IMAP server name reference provided by Microsoft.

Outgoing (SMTP) email server: You can get this information from your ISP or administrator. Usually, an outgoing email server address is in the format of mail.contoso.com or smtp.contoso.com.

The servers are set up to use the server name (mail.contoso.com) followed by a colon (:) and then the port number followed by another colon and then another number (usually 1). If the server name is valid, you will only want to change the number between the two colons.

Note: This can be done for accounts that use POP3 of IMAP for incoming email and SMTP for outgoing email. You may need to contact your email provider to determine what ports they support for POP3/IMAP and SMTP.