How to fix error “Microsoft Outlook cannot sign or encrypt this message” when sending email?

Sometimes, when you try to send an email through Microsoft Outlook, you might encounter the error message: “Microsoft Outlook cannot sign or encrypt this message.” This issue usually arises due to certificate problems with local S/MIME settings. Don’t worry—this guide will help you resolve this issue in both Outlook for the Web and Outlook for the Desktop. Please see How to Fix Microsoft Outlook Not Syncing Issue, and How To Encrypt Email Sent In Microsoft Outlook.

Also, see How to change your password in Outlook Web Access, how to encrypt Microsoft SQL Server Traffic, and how to Remove a profile on outlook.

Error Message Breakdown

When trying to send an email, you might see this error message:

Error Message: Invalid Certificate. Microsoft Outlook cannot sign or encrypt this message because there are no certificates which can be used to send from this email address ‘[email protected]’. Either get a new digital ID to use with this account, or use the Accounts button to send the message using an account that you have certificates for.

This message indicates that Outlook is trying to use local S/MIME settings and certificates, which may not be properly configured.

Please see these related guides: How to Block ZIP/RAR Attachments in Outlook, How to stop Outlook from opening links in Edge Browser, How to Recall an Email in Microsoft Outlook, How to change Windows 11 and 10 default mail app to Outlook, 5 Steps to Fix Outlook continually prompts for passwords on Windows 10 and 11.

Fixing the Issue: Use Outlook Web

Open your web browser and go to the outlook webmail platform. Log in with your email credentials.

Try sending the email through the web interface. Sometimes, the web version doesn’t encounter the same certificate issues as the desktop version.

Please read How to Share Microsoft Outlook Calendar on Desktop and on Web.

Outlook for the Desktop

Launch Microsoft Outlook. Click on the “File” menu located at the top left corner of the window.

At the bottom of the menu, click on “Options.”

In the Options window, select “Trust Center” from the left-hand menu, and click on the “Trust Center Settings” button on the right.

Encrypt Email

In the Trust Center window, click on “Email Security, and uncheck the following options:

• Encrypt contents and attachments for outgoing messages

• Add digital signature to outgoing messages

Click “OK” to save the settings and exit the dialogs. After adjusting the settings, try sending the email again.

Conclusion on fixing Microsoft cannot Sign Messages

By following these steps, you should be able to resolve the “Microsoft Outlook cannot sign or encrypt this message” error. Switching to Outlook for the Web can be a quick workaround, while adjusting settings in Outlook for the Desktop ensures a more permanent fix.

Remember, the key is to ensure your email security settings are correctly configured and that the necessary certificates are available.

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