Acceptable common printer friendly sizes:
6.5 x 9
6.5 x 12
8 x 6.5
8 x 10
8.5 x 11
9 x 11
9 x 12
Example of how to prepare the card:
Only other printing is concern is sag. If you use paper too thin and it sags too much it could be rejected.
Take them into your Postal Office they will be delighted to have someone local to direct customers to for printing them and preparing them. Don't send your client.
Plus the post office is hurting for business they are very positive about this.
You must separte them by carrier, count them, rubber band them and complete some forms explaining where and to whom on the route to deliver.
Never complete them online. Always print the routes online but pay at the post office. You can get them to deliver only businesses if done correctly for your sign shop. The online prints will include many many addresses you will not want and handling them personally you can communicate to what I have found to be very willing Postal Workers and Managers the exact addresses you would like.. for me that is businesses only.
Results vary and the day of the week for delivery is Tuesday for us. Ask you route carrier what kinds of mail he delivers most on each day of the week. They know and if they will share you can target the day that your piece will have the best chance to stand out.
Good Luck
Have always gotten a bigger return than investment from each EDDM piece we've sent.