Is your classic thin envelope, like a utility bill, invoice, or birthday card that arrives in your mailbox. It is required to be under 5mm thick, under 30-50grams and be PAPER only*.  You can mail this anywhere in the world. Postage based on weight and destination.

This is very similar to standard lettermail but is for bigger and thicker mail like quarterly reports and legal documents. It requires to be under 20mm thick and under 500g.  Size is required not to exceed 380mm (L) x 270mm (W) x 20mm (D),  and be PAPER only*. Postage varies as it is based on weight and destination.

OTHER “NON-STANDARD - OVERSIZE LETTERMAIL”  Is identical to OVERSIZE LETTERMAIL for size and weight requirements, however, it is the service that allows “non-paper” contents when mailing within Canada. Examples of such items includes things like jewelry, soap, enamel pins, guitar strings, Lego, and so much more.

Requirements:

Minimum: L 140mm   W 90mm  D .18mm    3g  

Maximum:  L 380mm  W 270mm    D 20mm   500g       

Postage based on weight: Rates in effect as of January 13th, 2025.

3g - 100g     $2.61  

100g - 200g   $4.29  

200g - 300g  $5.98    

300g - 400g  $6.85

400g - 500g  $7.36 

over 500g  = parcel rates  

If you require tracking you can send the Slotbox as OTHER lettermail with Registered Mail add on option. There is the added bonus of proof of delivery with signature and up to $100 insurance. Often a cheaper option than regular or Expedited parcel.

It is an additional $13.15 on top of your Oversize lettermail postage.

For example: Box mailer under 100g and fit the 20mm slot = $2.61 postage + $13.15 RM fee = $15.76+ G/HST.

Must be done in person at the post office.

Boxes are allowed as “OTHER - Non-standard/Oversize” in Canada, but does the box need to be in an envelope?

Yes, and maybe…

If the box is too small to meet the length and width requirements, then yes, it is required to be in an envelope that is minimum of 140mm x 90mm in size.

Larger boxes that satisfy length, width, depth - The Canada Post website states the envelope is a requirement of “Machinable Mail” for ease of box into / protect the mail processing machinery.

…however Canada Post has been known to accept a box not in an envelope when taped securely closed. No envelope is at the discretion of Canada Post. So, if you wish to mail without an envelope, have a CP associate accept it into their system. If you use an envelope, you can skip the post office line-up and drop off in a street receptacle and your customer will have a nice little gift box now too!

You can deposit the box at your local post office or in the large red street receptacles. 

Unfortunately, Canada Post intentionally designed the community hubs outgoing mail receptacles to not accept oversize lettermail so that they will not get overstuffed with mail too quickly. The red metal rain guard is on such an angle that a box, even a box under 20mm will not fit.

This leads to some confusion. Know that the “20mm” size requirement is for the processing of mail in machinery at the CP facilities, not for the receptacles where you drop your mail off.