Does a 2012 DC generate exchange certificates on Exchange 2007 server?

Question

The reason I ask is because we have a 2008 server environment with a few 2012 servers in the mix, one being a DC. It is time to renew our self-signed certificates on our exchange server and when I attempt to do this via the Get-ExchangeCertificate command,
I get a warning stating the following: 
WARNING: This certificate will not be used for external TLS connections with an FQDN of 'mail1.mymail.com.COM' because the self-signed certificate with thumbprint 'AAA-THUMBPRINT-AAAAAAA' takes precedence.
On further investigation I noticed we have a certificate that I do not remember from years past nor do I ever remember getting that warning message before. We have not used third party CA's. Notice the items in bold, the certificate is an enterprise cert, not
self signed and linked to our 2012 DC. There appear to be no services assigned to it but we still get that warning.
AccessRules : {System.Security.AccessControl.CryptoKeyAccessRule, System.Security.AccessControl.CryptoKeyAccessRule}
CertificateDomains : {EXCHANGESERVERNAME.DOMAIN.NAME}
HasPrivateKey : True
IsSelfSigned : False
Issuer : CN=DOMAIN-DC3-CA, DC=DOMAIN, DC=NAME
NotAfter : 12/31/2014 4:36:02 PM
NotBefore : 12/31/2013 4:36:02 PM
PublicKeySize : 2048
RootCAType : Enterprise
SerialNumber : 2D00XXXXXXXXXXXXXXXXXXXXXXX
Services : None
Status : Valid
Subject : CN=EXCHANGESERVERNAME.DOMAIN.NAME
Thumbprint : 4886XXXXXXXXXXXXXXXXXXXXXXXXXX
So my question is two-fold, why is this certificate here (was it generated by our 2012 DC) and will it effect anything when it expires? If so, how do I renew it?

Answer 1

OK, so it is normal. We did add the 2012 DC to our existing server environment later on. It is not our primary DC.
So, since there are no services assigned, when it expires in a few days, there will be no effect? If there will be an issue, how do I go about renewing it exactly?
I am not aware of us requesting an Enterprise CA, however our previous manager could have. I am not familiar with the process.
Basically, I ignored the "This certificate will not be used for external TLS connections warning" and created and enabled new self-signed certs for our mail server. The warnings in the event log that the old certs are about to expire have
stopped. So that should be that then right?
So as of now, we show 3 certificates, one being the enterprise one I mentioned which will expire in a few days. (Is this normal or should we just have one self signed cert that has all services?) I have a feeling this configuration isn't optimal.
Thumbprint                                
Services   Subject
2038XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX  ...WS     CN=WMSvc-MAILSERVERNAME
B52BXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX  IP..S      CN=MAILSERVERNAME
4886XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX  .....        CN=MAILSERVERNAME.DOMAIN.NAME