Just installed and configured SQL Reporting Services 2008 with ConfigMgr. 2007 R2 SP2 this morning. Everything went smoothly except for one minor detail; I got an error in my mail subscription:

Failure sending mail: The message could not be sent to the SMTP server. The transport error code was 0x800ccc15. The server response was not available

After a little investigation it turned out that the McAfee firewall was causing the problem. From the local firewall log file we could see these entries:

3/22/2010 9:57:12 AM Blocked by port blocking rule C:\Program Files\Microsoft SQL Server\MSRS10.MSSQLSERVER\Reporting Services\ReportServer\bin\ReportingServicesService.exe Anti-virus Standard Protection:Prevent mass mailing worms from sending mail

After tweaking the rules at the firewall server to exclude the process ReportingServicesService.exe everything worked as expected.