EWS issues - Could not establish trust relationship for the SSL/TLS secure channel.

[exchange_noob]

Hi,

First of all, I'm total noob for Exchange services. I have deployed Exchange 2013 in my lab to test one software integration via EWS. All the time, I have "Invalid credentials (401)" error, and I could not troubleshoot in detail. So I downloaded EWSEditor to test connection to my local Exchange server. After testing Exchange services configuration, I'm getting following:

Message: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel.
Exception details:
Message: The remote certificate is invalid according to the validation procedure.

Now, since I don't have enough skill with Exchange nor CA, what do I need to setup (regarding certificates) on client side so EWS connection would work properly?

[Ossian]

Make sure the certificate (or the root CA in the issuing chain) is trusted by the other side. Where did you get the certificate?

[exchange_noob]

I just opened EWSEditor and made Exchange service. When I specify Service URL (https://exchange.domain.name/EWS/Exchange.asmx) I receive SSL error. On Exchange Admin center, I can see certificates (Microsoft Exchange Server Auth Certificate, Microsoft Exchange, WMSVC) which are all Valid.

Do you have any suggestion what could I try to test?