MS Outlook is one such popular client, but many complained of experiencing certain problems. For instance, they get An error occurred in the underlying security system. The supplied handle was invalid when trying to send an email in MS Outlook. This error prevents users from accessing Outlook data files, as well as sending emails.

How can I fix Outlook security system errors?

1. Restart your Internet connection

Firstly, a quick fix you might want to try is to restart your Internet connection. Sometimes, your ISP might be having issues, therefore, you might want to consider changing your ISP, as well. However, to check if the connection is really down, try to access a website in your browser. If you’re unable to access it, then the issue is obviously due to a connection error. So restarting the Internet connection might fix the problem.

2. Create a new Outlook profile

By default, the above steps will create an IMAP account, if the email server supports it. However, you can also manually configure your email account, but beforehand you need to locate your Outlook data file. To do that, follow these steps: Also, you can configure your email account manually, by doing the following: Alternatively, you can back up your data file and delete your Outlook profile before creating a new one and linking it to the data file. Creating a new profile will remove all your settings, but it should fix the Outlook error in the underlying security system problem.

3. Set the Inbox folder

Alternatively, you can create a different folder that can be used to store your emails. SPONSORED This solution might be helpful since the Outlook underlying security system error can occur if the Inbox folder isn’t specified.

Ending all Outlook processes running in the background should solve the problem. However, if you still get the error, proceed to the next solution.

5. Switch off antivirus software

Alternatively, the antivirus software can be disabled by right-clicking its system tray icon and selecting a disable, pause, or exit option.

6. Switch off the Windows Firewall

7. Run Outlook in Safe Mode

Just like with other applications, Outlook’s Safe Mode can be used to resolve errors. Among them, the underlying security system issue.

8. Increase the Server Timeouts setting in Outlook

The Server Timeouts menu can fix interrupted connections issues and can help with sorting out the underlying security system error. To conclude, these are applicable solutions that should fix the Outlook error in the underlying security system so that you can resume sending emails. Currently, Mailbird is one of the most popular email clients given the many integrations with other apps like Google Calendar, Twitter, or Asana. This allows users to manage their emails from a single, unified console. Besides, the receivers can use any other email client and still be able to see messages sent over Mailbird. The tool does not require them to install additional extensions or plugins. If you have tried other troubleshooting methods or if you have any questions concerning this topic, let us know by commenting below.

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