I created a cert the other day for a customer so thought I'd share the Powershell command, you never know it might help!
New-ExchangeCertificate -GenerateRequest -Path c:\CompanyA.csr -KeySize 2048 -SubjectName "c=GB, s=London, l=London, o=CompanyA, cn=Mail.CompanyA.com" -DomainName Server1.CompanyA.com, Server2.CompanyA.com, Autodiscover.CompanyA.com, Server1, Server2 -PrivateKeyExportable $True
This cert will allow CompanyA to access external services to exchange, such as Exchange Active sync (EAS), Outlook Web Access (OWA), Autodiscover, Outlook Anywhere (RPC/HTTPS), etc…
Obviously in order to access these services you will need to setup ISA and publish the relevant rules. In this example Mail.CompanyA.com will be configured in ISA as a multiple path rule, allowing a single url for client access to services like OWA and EAS for example.
Written by Daniel Kenyon-Smith