Around the beginning of the year, we started the migration from an On-Site Exchange 2010 server to Office 365.
The on-site server had an alias of mail.domain.com, an SSL certificate was purchased that covered ServerName.Domain.com, autodiscover.domain.com, and mail.domain.com.
Halfway through the migration I changed autodiscover.domain.com to point to autodiscover.outlook.com both externally and internally on GoDaddy and our MS DNS Servers. Earlier this month, the migration was completed and I turned down and retired the on-prem server. Since users were comfortable with and knew the "mail.domain.com" url, I setup our web server to automatically redirect to the Office 365 webmail servers (http://mail.office365.com).
Now users are receiving a Security Alert periodically and when they start Outlook that the SSL certificate is incorrect for mail.domain.com (below). As far as I know, nothing should be configured to use the old mail server, a capture of the Outlook Connection Status is below as well.
Image may be NSFW.
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Image may be NSFW.
Clik here to view.
Jonathan N.
