Believe it or not, we get this question a lot.
When setting up #10 Envelopes for printing, our general rule of thumb is to put the logo 3/8″ away from the left and top margin. The press needs a minimum of 5/16″ for a gripper and we generally pull from the short edge of the envelope where the logo is. So this is the minimum the distance any printed element needs to be set away from the edge.