I purchase these envelopes for the obvious reason of not having to lick envelopes but I find myself adding tape to seal the envelopes as they are opening while on my desk. I can't imagine what happen when it gets to USPS and the sorting machines.
We have been using the Staples brand envelops for a while now and I think this will be the last time. the self sealing strip is about half the width as it was on my last order and they aren't staying closed as well now. It also appears that the "security" print on the inside is much lighter than it used to be.
Although I like the peel & stick flap I would NOT recommend this product to someone who was serious about security. A security envelope should allow me to place a check in without having to fold the check or place something over the account number to prevent potential account information theft but you can easily read thru this envelope.