Hi,
i never tested in with a linux 64-bit domino server (neither 8 nor 9).
Can you see the mailscan task (using sh ta at the console)?
Perhaps you can set the following variables in your domino-server notes.ini?
MailScan_DebugLevel=3
MailScan_ExtDebugLevel=3
MailScan_logToFile=2
Is there any output at the console or in NOTESDATA\mailscan.log?