I drilled a hole in the top of the mailbox and pump it full of water from my garden hose before taking the mail out. I then shovel the wet mail out the box into a wheelbarrow and leave it in the sun for a couple of days to dry. Then I take it inside, put the iron on high-steam setting and iron each piece for about 15 minutes. Then (just to be sure) I put it in the microwave for 5 minutes on high. Only after all this is done do I dare to open it.
I'm really getting sick of junk mail. But on the plus side, most of our bills are unlegible now.