I am completely new to SSL/TLS and would appreciate any help you guys could give me.
To give you some background info, our company website is hosted externally by our ISP, however our email is redirected by our ISP to a mail server which is located at our offices.
We use communigate pro.
We have a customer who until recently had no problems in sending us emails, however, we now have a situation whereby their mail server is stopping emails being sent to us.
I believe the root cause of the problem is that when SSL is enabled, the customer's mail server recognises this and so attempts to send email using TLS encryption. However, the SSL certificate used by our mail server is self-signed and, as a consequence, is rejected by the customer's mail server.
The error message returned to our customers is:
(Certificate rejected over TLS. (sslv3 alert unexpected message))
If SSL is disabled on our mail exchange server, we can receive emails from our customer.
I have acquired a Free Trial SSL certificate issued by comodo, however, it appears that this is still causing a problem. The Certificate is generated for ourdomain.com.
Should this be something like mail.ourdomain.com or should we purchase a wildcard SSL Certificate? I apologise if I have not worded this very well but any advice or other suggestions would be greatly appreciated.