Board backed envelopes are a great way to send documents through the post that you do not want creased or damaged.  The envelope has a heavyweight piece of card board forming the back of the envelope providing a strong structure to the envelope. These envelopes usually come with a pre-printed text of "Do Not Bend" ensuring that anyone handling the envelope and contents is well aware that it should be treated with care and not folded. Available in either white or a buff/brown manilla with a self sticking press seal flap or a gummed flap that needs to be moistened to make it adhesive.