Choose the class that best suits your budget and project delivery time. Go with Standard Mail if Your Project is NOT Time Sensitive: You can expect Standard Mail delivery typically in 10-15 days, so if you have a rapidly approaching event or expiration date in your promotion NEVER choose Standard Mail. Standard Mail is less expensive in postage, so this option might be suitable for your needs if you have enough time for your promotion. However please note that standard mail not only takes longer, but it is also not forwarded and not returned if “undeliverable”. It merely goes into the USPS recycling bin. Go with First Class Mail if Your Project IS Time Sensitive: If you have a time-sensitive project choose First Class Mail which delivers typically within 1-4 business days and automatically includes return service for undeliverable addresses at no charge, specifically: if your party has moved, for a period of 1 year OR if it’s undeliverable, it will be returned to you. If you need more information about the Direct Mail service click on this link https://www.4over4.com/printing/category/direct-mail-services