The Standard version runs across three servers, one each for management, messaging and security. The Premium version runs on four servers and adds a database server option for business applications.

Microsoft announced earlier this year that it was introducing the option to purchase single client access licenses (CAL) for either platform. Previously, users had to purchase CALs in blocks of five.

In addition, the CALs will apply to copies of Windows Server, SQL Server and Exchange Server running outside the Essential Server environment.

The pricing for SBS 2008 Standard is $1,089, which includes five CALs. Additional CALs are $77 each. The Premium version is priced at $1,899, and additional CALs are $189.

The Standard version of ESB 2008 is priced at $5,472, including five CALs. Additional CALs are $81 each. The Premium version is priced at $7,163 with additional CALs priced at $195.