So I guess you are using Mac OS X Mavericks Server.
Someone which faced same issue wrote an answer on his blog : here.
سؤال
I am getting this email about every six minutes, day and night:
The following certificate is about to expire on your server, server.xxxxxx.private: Name: server.xxxxxxx.private Code Signing Certificate Expiration Date: December 14, 2013 10:13:03 PM PST
I can't find this certificate on my server to update it. Would anyone mind pointing me in the right direction?
المحلول
So I guess you are using Mac OS X Mavericks Server.
Someone which faced same issue wrote an answer on his blog : here.