Receiving error - Sending' reported error (0x800CCC0F) : 'The connection to the server was interrupted. If this problem continues, contact your server administrator or Internet service provider (ISP).'

Hi @Jack Riegler 
Thank you for reaching out to Microsoft Learn Q&A!  
***Please understand that our forum is a public platform, and we will modify your question to cover your organization domain name in the description. Please notice to hide these personal or organization information next time you post error or some information to protect personal data. ***    
Based on your description, it seems you're encountering the 0x800CCC0F error when using Outlook with a POP3 account. This is a well-known issue, and fortunately, Microsoft provides two official workarounds to help resolve it. I'm happy to share them with you below. 

Workaround #1:  If you are getting the errors 0x800CCC0F, it could indicate that there’s a problem with the App Password with your POP3 email provider.  This could happen on Windows 10 or Windows 11.  You could create a new App password to check whether the cause is come from App Password or not 

Workaround #2: Microsoft has identified that TLS 1.3 may trigger the 0x800CCC0F error in Outlook on Windows 10. Their testing shows that TLS 1.3 works correctly with Outlook on Windows 11. If you're using Windows 11, you can double-check whether TLS 1.3 is enabled by following these steps: Windows +R > inetcpl.cpl > Advanced > scroll down to the "Security" section to ensure that TLS 1.3 is checked.
To better understand the scope of the issue, could you please confirm whether all affected users are on the same version of the operating system, or if there are differences? 

For more details on these workarounds, please refer to the official Microsoft Support article: Outlook IMAP or POP server unexpectedly terminated the connection, and the server was interrupted - Microsoft Support 

Additionally, here’s an example of another user experiencing a similar issue: The connection to the server was interrupted - Microsoft Q&A 

If the issue persists after trying the above workarounds, could you please check whether the same problem occurs when using a different email client, such as Thunderbird? 
Note: Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above.  

This will help us determine whether the issue is specific to Outlook or related to the email server configuration. 

I hope this helps clarify your situation and guides you toward to a solutions. Please feel free to ask if you have any other questions.   

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".         

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread "