Using Custom Envelopes

This feature is exclusive to certain customers. Upgrade to the appropriate Print & Mail Edition to gain access.

Additionally, Custom Envelopes are currently only supported for letters; they are not available for checks. To get started with creating letters with custom envelopes, refer to our letters documentation.

Envelopes must be created, ordered, and printed before they can be utilized. Create and manage your custom envelopes from within the Lob dashboard.


Custom envelopes are 9.5" x 4.125" and can fit up to six tri-folded 8.5" x 11" sheets.

If you'd like to use a custom envelope with your mail piece, you will need to set the custom_envelope parameter in your POST call to to the desired custom envelope ID, which can be found in your dashboard. If a letter is created with a specified envelope ID that is not in stock, the letter request will be rejected. If a letter is created with a specified envelope ID and is 7+ sheets, the letter will be sent instead in a blank, flat envelope, and the custom envelope inventory will not be decremented. Additionally, custom envelopes have an expiration date, which ensures the envelope's integrity.

Reference our custom envelope template to see where you can put your design elements. Additionally, custom envelopes will not be printed outside of the safe zone.


The envelope window is where your recipient address information will be visible. Reference our letter template to ensure that your recipient’s address is visible. No design within the envelope window will be printed.


Postage will be placed in the upper right corner of the envelope. No design will be printed in this space. Refer to our custom envelope template for stamp placement.


USPS prefers that return addresses are placed in the upper left portion of the mailpiece, on the side of the piece bearing postage. USPS does not require that all mail include a return address; however, mail sent without a return address cannot be returned.


Envelopes can be purchased as one-off orders or through auto-reordering. The minimum order quantity for custom envelopes is 10,000 envelopes per artwork design.

Note: Typically, any first-time order process for new envelope designs can take more time for quoting, production, and shipment. Allow up to two weeks for any new design orders to be fulfilled.


When the auto-reordering function is turned on, a new order will be submitted whenever the remaining envelope quantity in inventory falls below 20%. A confirmation will show the reorder quantity and price that will be charged.

Given that custom envelopes have additional lead times, we recommend enabling auto-reorder for envelopes that will be continuously utilized to ensure there will be no risk of running out.


Order details will be populated in the order history window once the order is submitted. Expected date provides a rough estimate of when envelopes will be available, while an email confirmation will be sent to you when envelopes are actually ready for use.


Return to the dashboard at any given time to view existing order designs, the number of remaining envelopes, and the number of orders that are still outstanding or fulfilled. Inventory will decrease with each API call made that specifies a custom envelope.