Do you use your knife for opening letters, and if so, which blade?

[Mora2013]

Depends on the knife I have. If it's a stockman, it's the sheepfoot. Often times it's one of the smaller secondary blades.

I don't dedicate a blade for mail or package opening, but I do try to dedicate a blade for food.

I don't really worry about dulling the blade with paper. IMHO every use wears on the edge somewhat.