Private Message Organization and Rules

I saw that someone posted a similar subject regarding this matter, but it looks like it had just died off and I believe it should at least be revisited. I was just going on a rant with a server member about how DMs just collect there and the only method of organization is deleting them. 

A function such as categories to separate the users intro groups, i.e;

{Server_1}

person1
person2
person3

{Server_2} 

person1
person2

etc...

If this is something feasible, could I recommend simple rules, i.e. if DM from user on Server_x is received add to Server_x category.

If that is too much to develop or there are variables that prevent this from happening then could you at least add a pin user function so you don't have to strain your eyes looking for the UN if your 'inbox's' volume is quite large.

Kind Regards,

Stux