Outlook Internet Security Warning

I am using Bluehost to host my website and I added an account in Outlook to get my email from my website domain email account. When I open Outlook, I get an Internet Security Warning message. I Install the Certificate as a Current User or Local Machine and neither gets rid of this message. Viewing the certificate shows that it was issued by Avast. How do I stop these messages from popping up?

Try: https://support.avast.com/en-ww/article/91/#pc