A logged-in user performs a scan to e-mail that results in received messages being forwarded to the recipient's spam folder.
A PE-released version of firmware 030.079 or later, is known to address this specific issue.
Check the printer's current firmware level.
This can be found under Settings > Reports > Device > Device Information > Base.
Contact Lexmark Technical Support and reference this KB topic to request updating to this firmware version.
LEGACY ID: SO8165
The general Scan to Network folder application information is found here.
Scan to e-mail primary escalation KB