As all reviews say, Mailbox Peak is really no joke. It is a 2.5 mile Death March for the unprepared, and an ass kicking workout for the prepared. Don't let the mere 2.5 miles fool you.
You walk up the forest service road about 1/2 mile until you get to the official entrance to Mailbox Peak trail head next to the notice board. Be very carefull to take the entry immediately from the notice board, as once i(and many others) went straight and wondered in the forest for 1.5 hrs trying to find the trail head. The first 1/4 mile of trail you are meandering in a forested area with a few nice cold creeks running through. You will find these useful to soak your tired feet when you get back down. This little jaunt doesn't last long as the trail goes into full business mode with the quickness. No transition, no feeling out process, just you looking at this straight up, root stepped, steep as hell thing saying "DAMN!"
Welcome to Mailbox Peak.
This part of the trail you are under the tree canopy and more often than not you will run into some serious mud, roots, logs and assorted things you have to climb over or around. The switchbacks are more like s-turns as they seem to not want to give you much of a break and just push you up up up the hill. If anyone says "it gets easier" or "you're almost there"...they are lying :)
After what seems to be an eternity, eventually you will break out of the tree line and will finally have some nice scenery with lots of flowers and big views, but the most apparent view will be the huge boulder field in front of you. If you are not up to the scramble challenge, just follow the left edge of it, the trail will be apparent. Plenty of false summits, but I do think once you are out of the tree canopy, the going gets much easier and even if it is muddy, it seems there is more rock mixed in for better grip. Eventually you will reach the mailbox.