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EnvyPak is the only clear poly envelope known to be machine insertable

Many manufacturers have not established specifications. That said, EnvyPak clients have been successful with the following list of brands:

  • Pitney Bowes (FlowMaster and other models)
  • W+D Mail Inserter
  • Standard swing-arm
  • Bell & Howell (MailStar, Master Mailer, and other models)
  • Kirk-Rudy
  • Buhrs
  • CMC
  • NeoPost
  • Mail Crafter

General tips and info:

  • Poly will create static which can be reduced with tinsel
  • Many EnvyPak clients exceed 7,000 pieces inserted per hour
  • If you are having trouble feeding the envelopes try building a small incline at the edge of the feeder with painter’s tape
  • Store envelopes in a climate-controlled environment during periods of excessive heat
  • Fan each stack of envelopes as you are unboxing

Insert Size:

Lettershop specifications can vary slightly. Most require the outside dimensions of the envelope to be 1″ wider and .5″ taller than the insert.



Automated Sealing

Standard EnvyPak envelopes (NOT eligible for automation letter postage) can be sealed with peel-and-stick tape, wafer seals, or glue. Wafer-sealing attachments can automate tabbing on certain inserting machines.

Automation Letter Rates (ALR) EnvyPak envelopes have specific USPS sealing specifications. Wafer seals are an option for automation letter rates. EnvyPak envelopes can be manufactured with peel-and-stick tape or without tape for glue sealing in your letter shop.

1. Glue Seal

  • Melting point: Poly will distort if the glue is extruded beyond 280 – 300 °F
  • Contact your sales representative for glue seal supplier information
  • If the glue overheats / sits in the pot for an extended period of time it will yellow
  • The below picture shows a FlowMaster inserting an EnvyPak. The sensor is circled in purple and the glue head is in red.

USPS Automation Approved Glue Seal Specs Option One: (5) 1″ glue lines equally distributed along the length of the flap ending within .25″ of the leading edge, trailing edge, and bottom edge of the flap.


Option Two: (1) continuous glue line within .25″ of the leading edge, trailing edge, and bottom edge of the flap


Glue-sealed mail pieces that do not meet the above specifications will not qualify for automation letter postage.

2) Automated Peel and Stick Tape Liner Removal

  • EnvyPak envelopes can be manufactured with peel-and-stick tape
  • Tape liner can easily be removed by hand
  • Many EnvyPak clients automate peel-and-stick liner removal with a waste suction hose
  • A shot of air can be blown across the flap to assist the suction hose

3) Wafer Seals

  • Are eligible for automation letter rates
  • Many EnvyPak clients attach tabbing machines to affix 2 wafer seals inline

Edges can be printed on either or both sides of the envelope.

As the insert shifts from left to right the print must prevent a clear gap from occurring. A clear gap occurs when one can see through one side of the envelope and out the other.

Any print that prevents a clear gap can be compliant. Contact your sales representative for more creative approaches to meeting USPS requirements.


Standard EnvyPak envelopes often fall under DMM poly wrap guidelines. The material (not the envelope) is approved as a poly wrap.

EnvyPak ALR (automation letter) envelope guidelines do not fall within the DMM. DMM section 201.2.1 states “A letter-size piece is nonmachinable if it has an exterior surface that is not made of paper.” USPS issued an EnvyPak ALR-specific approval letter which overrides 201.2.1. The approval letter and a sample piece MUST be presented to Business Mail Entry (BME) acceptance personnel to pre-verify and drop mail.

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