Exchange SSL Certificate name Mismatch

Dear Techies,

I have Exchange 2010 Hub & Cas in my environment. Recently i have purchased SSL Certificate from third party CA Digicert. My local domain name mail.xxx.int is not included by Digicert in SSL Certificate.  After installing new SSL certificate on IIS our internal outlook 2007 users are receiving Security Alert similar to the below image. 

My companies local domain name is mail.xxx.int. External domain name webmail.xxxx.org. 

Any immediate help will highly appreacited,

Cheer's

Gowtham.