Perhaps one of the strangest things I have ever observed with browser differences.
I am able to retrieve mail via MEWebmail using Mozilla Firefox (Quantum) & IE 9 like this:
https://mail.mydomainname.com/MEWebMail ... login.aspx Works great!
When I copy the URL from above, then try to login with MS-Edge, site first asks for Client to approve a client-site Cert. from MS-Organization-Access, valid for 10-years. I click OKAY which then yields "403: Forbidden - Access is Denied" message.
Chrome is identical, except it does not ask for approval of the Certificate.
Perhaps this is a setting on the Server side, a check box to require clients to provide a certificate? I've looked and looked, but not found an improper setting. Any ideas would be greatly appreciated.