Exchange & RDS internetaccess multiple servers

Good afternoon,

I've setup a new server with 2012r2 as a host. There are three VM's:

VM1 is the DC
VM2 is the RDS
VM3 is the Exchange 2013.

I've used http://msfreaks.wordpress.com/2013/12/09/windows-2012-r2-remote-desktop-services-part-1/ as a guide for RDS.

The internal AD domainname is corp.domainname.nl
The external e-mail domainname is domainname.nl

I've created the DNS forward lookup zones rds-gateway.domainname.nl and exch.domainname.nl pointing to the coresponding ip-adresses, so we can use these later to access from the internet.

The RDS servername is RDS1.corp.domainname.nl
The Exchange servername is exchsrvr1.corp.domainname.nl

In ECP (servers, virtual folders) I've used the same internal and external url for accessing the server (all names in the list): exch.domainname.nl

I've registered a certificate at Comodo's with these names:
rds-gateway.domainname.nl
autodiscover.domainname.nl
exch.domainname.nl

We have one public IP-address and use a Vigor 2960 as firewall.

Problem one. Outlook still pops up with an error message that the name on the certificate is not the same one as Outlook is trying to access. Outlook points to exchsrvr1.corp.domainname.nl. I can't figure out what to change and where to change it, other than putting a fourth name on the certificate.

Second: I've created two port forwardings on the firewall. IP Port 25 and 443 are forwarded to the Exchange 2013 machine. I'm not sure how to grant internet access to the RDS since this server also uses https for connecting to it. How do I solve this?

Björn