Do I select a booklet or catalog style envelope?
If you’re mailing a few personal or full rate letters, the type of envelope does not effect the cost of mail services or postage because you’ll likely assemble the mail piece yourself.  If you are managing a project over 1,000 pieces, you’ll want to consider automating insertion.
A booklet envelope open on the long side and inserts can be automated,  while a booklet style envelope, opens on the short side and can not. Typical insertion equipment runs anywhere from 5,000 to 10,000 pieces an hour depending on the system and specific of the application.   Hand insertion typically runs from 250 – 500 pieces an hour.
Time = Money, so if you’re planning a mailing over 1,000 pieces you’ll want considering selecting a booklet style envelope.   You’ll see loads of savings in the cost of mail services, which can run in the thousands of dollars based on the size of the campaign.