First-Class and Certified Mail Options
Flat Mail
Higher Page Counts Made Easy
LetterStream’s Flat Mail options let you send larger documents—like welcome packets, legal sets, board books, and marketing kits—in professionally printed, addressed, and USPS-mailed flat envelopes. We handle printing, inserting, and mailing for you, so bulky or multi-piece mailings go out accurately, on time, and with the polished presentation your recipients expect from a trusted print-to-mail partner.
First-Class Flat
As Low as $2.67 Each
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Send up to 75 printed pages
Double-sided printing available (duplex) -
Documents arrive unfolded
No control over USPS handling -
Mix color and black-and-white printed documents
Save costs while keeping visual impact -
Add return envelopes — get creative!
Explore our multiple letter options
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Certified Flat
As Low as $9.96 Each
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Send up to 75 printed pages in a single envelope
(automatically updates to parcel after 75 pages) - Track your documents on LetterStream.com or USPS.com
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Your documents arrive unfolded
(except for what the Postal Service might do)
Electronic Return Receipt (ERR) Option as Low as $12.78 each
Flat Mailing Highlights
Send multiple documents in a single 9” × 12” envelope. Whether you need economical First-Class Mail or fully trackable Certified Mail, our Flat option makes it simple to send high-page-count documents with confidence. You can mix color and black printed pages, include return envelopes, or even choose postcard stock for certain inserts. This versatile flat packet handles up to 75 double-sided sheets.
Frequently Asked Questions
What is Flat Mail?
Flat Mail refers to large envelopes that can accommodate unfolded documents. The standard size for Flat Mail is 9” x 12”, allowing you to send documents without folding them, which is ideal for presentations, contracts, or any important paperwork.
How many pages can I send in a Flat Mail envelope?
Flats can hold 1-75 sheets of paper. If your document includes more than this, you can choose duplex printing which would allow you to send a 150 page PDF document in these envelopes.
What is the cost of sending Flat Mail?
The cost for sending Flat Mail starts at $2.67 each for First-Class Mail and $9.96 each for Certified Mail (without signature receipt). Prices may vary based on additional features or options selected.
Can I track my Flat Mail?
Yes, you can track your Flat Mail if you choose Certified Mail. Tracking information will be available in your LetterStream account, and you can also track it on the USPS website.
What types of documents can I send using Flat Mail?
You can send a variety of documents using Flat Mail, including contracts, presentations, reports, and any other important paperwork that needs to remain unfolded.
Do I need to supply an address list for Flat Mail?
Yes, you will need to provide a CSV data file or address list when creating your Flat Mail job. This ensures that your documents are sent to the correct recipients.
Will my job automatically upgrade to Flats if it’s too long?
Yes. If your mailing exceeds the standard outer envelope capacity (over 14 sheets), our system automatically upgrades it to a Flats envelope for you.
Can I staple or bind pages in a Flats mailing?
Yes! Stapling is available for flat mailings (not including FedEx mailings). This is a benefit to sending documents in the larger flat envelopes as stapling is not available for mailings that will be mailed in regular sized #10 outer envelopes.
Do you offer booklet-style binding for Flats?
No, booklet binding isn’t currently offered. If you need pages within the envelopes kept together, stapling is the best option.
