One of the email inboxes I use gets emails from Spam notification and when I click on “Release to Inbox” or “Report as Not Junk” to let an inadvertently temporarily blocked spam-quarantined message through, I get a little popup error message on the Mac Safari browser:

Screen Shot 2016-08-23 at 8.58.21 AM

Finally found a solution at the Microsoft support site: Mac users can’t release messages from Exchange Online Protection quarantine

To resolve this issue, follow these steps:

  1. Locate the Keychain Access program on the Mac. To do this, open Finder, and then open the Applications folder. The Applications folder contains a folder that’s named Utilities. The Keychain Access program is in the Utilities folder.
  2. Open Keychain Access, and then locate all certificates in the Safari dialog box that show as This client requires a certificate.
  3. Select the certificates that you located in step 2, and then delete them from Keychain Access.
  4. Restart Safari.