Removing an expired certificate MacOS Server 5.6.3

I apologize for posting twice. I could not find the server community in my original search. I will see if I can delete the other one.

I have a GoDaddy certificate for my website and email server that has expired and that I do not wish to renew. The device has a self-signed certificate that I would like to use in its place. I cannot remove the certificate because there are secure services using that certificate, mail among others. This does not pose a problem for my Macs to connect and retrieve mail, I am able to click "Continue" after I get the warning but my iDevices can not. Whether I click cancel or "details" nothing happens.

What can I do? I do not need to spend $200 for 5 domains. I'm not sure if I really even need one. How can I make it so that the services no longer depend on that certificate? I have searched everywhere in MacServer 5.6.3.