• Which labels do I need?
• Are there any dedicated printers that print Internet Postage labels?
• Why do I need to use fluorescent labels on envelopes?
• When can I use non-fluorescent labels?

• 3-Part Multi-Purpose labels (SDC-3100) contain labels for delivery address, return address, and postage which work for everything from letters to parcels.
• 2-Part Window Envelope labels (SDC-2300) do NOT contain the delivery address label as they are designed to work with windowed envelopes where the delivery address is visible through the envelope window.
• 2-Part Shipping Labels (SDC-2200) print the return and delivery address together on one label and the Internet Postage on the other. (Note: They cannot be used with the Stamps.com Shipping Label feature, only the Internet Postage feature)

Are there any dedicated printers that print Internet Postage labels?
Yes. Stamps.com offers the Stamps.com LabelWriter made especially for Stamps.com by DYMO™. The Stamps.com LabelWriter and other thermal LabelWriters by DYMO (EL60, LW320, LW330, LW330 Turbo, CoStar XL Plus, CoStar XL Turbo) support printing 3-Part (30383) and 2-Part (30384) Multi-Purpose Label Rolls and 4-Part (30387) Shipping Label Rolls. Please see our Postage Printers FAQs for more information.

Why do I need to use fluorescent labels on envelopes?
If you print postage directly onto envelopes, you don't have to worry about fluorescence. However if you wish to use labels with envelopes, the USPS® requires the use of fluorescent labels.

The fluorescent stripe replaces the Facing Identification Mark (FIM) on traditional envelopes. The FIM is the little barcode object next to the postage on all metered mail, and tells the USPS automatic feeding equipment if the envelope is upside down or right side up. If an envelope is upside down, the equipment turns it around so the automatic address reading equipment can determine the delivery address. The FIM must always be printed no greater than 1/8" from the top edge of the envelope, but the fluorescent stripe can be more than 1/8" from the envelope's edge and the machinery will still work. Because labels could be placed more than 1/8" from the envelope's edge, they need to have the fluorescent stripe.

The Postal Service does not allow you to use non-fluorescent labels on envelopes because it makes it difficult for their equipment to sort the mail. If you accidentally use a non-fluorescent label on an envelope your mail may be returned, just as if you sent a letter to an incorrect address with regular stamps. In such cases, no refund can be collected. Note that this requirement does not apply to packages or flats.

When can I use non-fluorescent labels?
You can use non-fluorescent labels when you are shipping flats and packages ONLY.