How to unstick and envelope

I have read to put it in the freezer for one to two hours and it should open:).

Unstick it from itself..... steam.... the snoops of the world do it all the time.

I just did some in the microwave with them balanced over a small container of water. You keep checking them until you can slowly pop or peel the edge back. I am also thinking about holding a steam iron over them for the same thing. Box of new cards and the envelopes had all gotten sealed up before use by the humidity in the storage area.

I put my envelope in the freezer for an hour, if I forgot to add something..When the envelope is back to room temperature you can close it again

https://lifehacker.com/5845438/open-a-sealed-envelope-by-putting-it-in-the-freezer

Steam it open

The steam should do the trick.