My simple style of posting is a clean white envelope printed with customers address & return address.
I want my greeting cards to arrive in perfect condition I always print do not bend on the envelope.
Keeping it simple keeps the costs down on posting, customers don't really want to be paying over the odds for to fancy packaging, also good for the environment to keep packing waste to minimum.
I do enjoy walking to the post box and putting a handful of envelopes into the post box, I always have a second check through to make sure they all have stamps on!!