Self-Adhesive Seal Envelopes are definitely the better way to go.  You will never have to lick another envelope again because no moisture of any kind is needed whatsoever.  We offer the “peel and stick” varieties that are completely self-sealing.  Just peel off the paper adhesive strip, fold the flap, and place in the mailbox.  Buy in packs of 50 or in bulk because all orders over $149 get automatic free shipping!