As per this MSDN , yes its not supported .

http://msdn.microsoft.com/en-us/library/ms165636(SQL.90).aspx

But there is a tweak 🙂

Copy DatabaseMail90.exe, DatabaseMailEngine.dll and DatabaseMailProtocols.dll into the MSSQL\Binn directory and execute below mentioned system SPs (in MSDB context)

dbo.sysmail_start_sp

dbo.sysmail_stop_sp

You are done .Actually these 3 files you need to copy from ENT edition or STD edition.

Regards