I work with sensitive documents and so I have to add tape but I also do not have 100% confidence in the sealing of the envelopes. I would accept it as a gift.
Used for mailing documents that should not be folded into standard sized #10 envelopes. Lacks consistency in quality for self-sealing. We order several boxes at a time and certain production lots require additional taping. Poor quality control.
Since the glue is weak these envelopes easily come open during transit and contents are then lost... If you must use these I recommend using tape to secure the flap and correct the problem. Good luck...