You have enabled checkbox "Log" under Spam Messages, Suspected Spam and SCL or Suspected Spam under Premium AntiSpam Actions. "Deliver to alternate recipient:" field is checked and is filled.
This is a known issue. Alternate recipient email address is incorrectly reported in the "RCPT TO" field under Premium Antispam log. Original recipient email address is also stripped from the log if checkbox "Prevent delivery to original recipient(s):" is checked.
This problem is fixed in SMSMSE 7.0.2. Upgrade to 7.0.2 to resolve this problem.
Symantec Mail Security for Microsoft Exchange 6.x