CNAME/redirect to OWA - certificate error

[OCdude]

We currently use a 2007 hosted exchange and we have a CNAME setup so that we can access it by going to: mail.companyname.com

We're about to move over to a 2010 hosted exchange (not sure if this is part of the issue), but trying to use the same CNAME method, seems to be throwing up certificate errors before going to the page.

Could someone let me know the best way to get around this (can it be done just by using DNS records?)

Thanks!

 

[OCdude]

Don't have any certificates

It works fine with Exchange 2007, so am I right in thinking this is due to some kinda of increased security on the 2010 platform?

Don't really wanna have to buy certificates to fix this :O