I played it before in the single player setting, seemed fun enough.

Is the item system like d2 where there is no "soulbound" items like WoW you can use them and trade them when you get something better?
Is there an Auction House/Mailbox?
What is the max level?
What is the best class to start out with?

yes item system is like on d2 no Wow shit

there is a mail box, no auction house(there is a huge trading section on the hellgate forums tho)

max lvl is 50 (atm)

donno the best class, u gonna start on normal which is easy and can be done with ease with any class

the items drop for every person ( so no fighting over drops) .. you can up your weapons and augment them ( rolls +skills for example ) they will release new items if you are a sub. with future patches .. their is normal/enhanced/rare/legendary/unique items ( also their is luck (mf) )
their is ingame email (you can attach one item to) no auction house yet*
max lvl is 50
depends on what your style is (mm or guardian is fun )

try a guardian or marksman

i am also!