Understanding the Best Postcard Sizes for Maximum Impact in Direct Mail Campaigns https://www.waivio.com/@waivio_postcardoffice/2rmutu-understanding-the-best-postcard-sizes-for-maximum-impact-in-direct-mail-campaigns Forget spammy or unwanted emails, the power in direct mail is in capturing attention and no form does it better than postcards, if you use the postcard dimensions wisely.