When submitting a postcard, the front of the postcard can be designed however you choose. The back however, should follow our templates, which leave designated areas blank for Lob to print the sender and recipient addresses.
If you are exporting an image for a printing proof, the way you usually would when sending images to traditional printers, then the trim lines should be unticked in your settings to ensure a sizing error does not occur:
Please also note that whether or not you export with “Bleed” will depend on how you built your template. If you already manually added the bleed (e.g. 4.25 x 6.25 artwork) then you should have that unticked as well.