I recently received a beautiful postcard from an RAoC member enclosed in a lovely envelope that was sent with a Forever postcard stamp (now valued @ 48 cents). I told her I loved that she used an envelope to house the postcard & was surprised one could get away with this as I assumed that postcard stamps could only be affixed to actual postcards. She said she's done this before without issues but it could be just a local post office being flexible thing. Her envelope measures about 6.4375" W x 4.625" H (apologies if my tape measuring is confusing, I never measured envelopes before)! So I'm wondering if any of you have experience using Forever postcard stamps on small-ish envelopes because my Google searches on what is permissible aren't helping. If you've successfully done this before - did you go by weight & add stuff in the envelope up to a certain limit or only include a postcard in the envelope? Because I recently bought small-ish V-Day cards with small-ish square-ish envelopes that are smaller than general b-day card envelopes - they measure about 5.1875" W x 5.0625" H & I'd love to know if I might experience any issues using Forever postcard stamps on them. They'll be super light but I can't say how light just yet because I may want to add some stickers. I'm tagging mail experts u/bluedecemberart u/feellikebeingajerk & u/SamathaYoga because I saw y'all's helpful recent responses to u/OkayFlan on mini mail questions. The attached pic shows the white envelope I want to use & the pink envelope is the one I received with the Forever postcard stamp. Thank you so much for y'all's help in advance! :)