SSL Certificates are now provided by LetsEncrypt. For now only the web server has been migrated; SMTP and IMAP will be moved over shortly.

Update 2017-02-28: SMTP and IMAP have been migrated to the LetsEncrypt certificates as well.

The StartCom SSL certificates will expire soon. For the last 10 hours web pages were served using a new set of certificates. However, Firefox reports the new certificates have been revoked. Reverted to old certificates for the time being.

Update: The problem was that Firefox does not trust newly issued StartCom SSL certificates!