I have my exchange 2019 server setup and working fine for passing mail. OWA and the wildcard cert I have works fine for OWA, mail clients, etc. No problems with normal mail flow, or utilizing the wildcard cert I purchased from Sectigo RSA Domain Validation Secure Server .
I do have an issue when attempting to telnet into Exchange using openssl in order to run starttls. I am able to get connected via openssl and I am passed a certificate from the exchange server, BUT it is not the certificate I am expecting. Instead of getting the wildcard certificate from Sectigo RSA Domain Validation Secure Server , I am getting a self signed certifcate. Which is why I believe my Ehlo after starttls fals with '501 5.5.4 Invalid domain name'.
Looking at EAC I have four certificates total
Name: Microsoft Exchange, self signed certificate, assigned services: SMTP
Name: Microsoft Exchange Server Auth Certificate, self-signed certificate, assigned to services SMTP
Name: Wild, Sectigo RSA Domain Validation Secure Server, assigned services IMAP, POP, IIS, SMTP
Name: WMSVC-SHA2, self-signed certificate, assigned to services SMTP.
Can I remove any of the self-signed certificates?
Is there a way to specify when using openssl to specify which certificate it should use?
my understanding is IIS needs the WMSVC-SHA2 cert....