If you actually read the message (click on it) it should be marked as read automatically. If you want some messages to automatically be marked as read, without you having to read them, you can do that with filters (eg, automatically mark all messages from jdoe@email.com as read when they're received).
Edited by Speedo (06/15/11 06:28 PM)
_________________________
Core i5-750 @ 3.2 Ghz [Hyper-212+ Cooling]
Gigabyte P55A-UD3 Mobo
8GB G.Skill DDR3-1600 @ 9-9-9-24
XFX Radeon HD6950
Creative X-Fi
Intel X25-M 80GB SSD
2x Hitachi 2TB HDD
Corsair 650W PSU
Dell 24" [1920x1200] LCD
Viewsonic 20" [1680x1050] LCD