Replacing letter box plate springs

Money_Grabber13579

OP again here.  Following all the helpful advice last year, I've now obtained a replacement and only getting round to fitting it now!

The next question I have is this - when I took the old letterbox off, there was some kind of adhesive or sealant holding it in place, along with the screws.  Is the adhesive/sealant necessary when I'm fitting the replacement letter box, or will the screws be sufficient by themselves?  If I should use adhesive/sealant, does anyone have any recommendations as to what I should use, both in terms of adhesive/sealant and specific product (it's a wooden door and metal letter box)? 

What I don't want to do it to end up gluing it to the door with some product which ends up being impossible to remove without cutting a hole in the door, if the letterbox ever fails again!