then do what I do. Take all their annoying envelopes and recycle them into envelopes that are actually useful.
Step 1. Take an annoying junk mail envelope (
Step 2. Very carefully take the envelope apart, you can usually manage this just be delicately pulling but have a craft knife handy incase it starts to tear.
Step 3. Fold all sides back on them selves so in effect you are turning the envelope inside out. Then glue sides together, carefully we don't want the envelope stuck together completely.
Step 4. Voila...one perfectly good envelope that can now be used for a far better purpose than sending off for loans or credit cards or the such like.
I use a wee bit of glue to stick the envelope down when I'm posting it off and if you're going to try to re-use envelopes that have your own address on them remember to black it out for your own data protection ;)
Keep doing this and you will never run out of envelopes for sending fun things like cards and letters or paying school dinner money or out of school subs :D And they look so cool too!