There are two size categories for Addressed Admail. First, there is what is called Short and Long, which is a mailing piece that does not exceed 156 mm X 245 mm and 5 mm in thickness. Short and Long mail can weight up to 100 grams. Secondly, there is what is called Oversize, which is a mailing piece that exceeds any of the dimensions for Short and Long, but does not exceed 270 mm X 380 mm and 20 mm in thickness. The maximum weight for the Oversize category is 500 grams.
The maximum width and length for Short and Long in inches is 6 1/8" X 9 5/8". Now, as you might be aware, 6" X 10" envelopes are a very popular size. However, they fall into the Oversize category. In some cases, there is as much as a $0.14 difference between the Short and Long and Oversize Addressed Admail rates. On a mailing of 10,000 pieces, selecting a slightly smaller envelope could save the mailer $1100 in postage costs.
As noted above, the maximum weight for Addressed Admail pieces is 500 grams. The cost to mail a 500 gram piece in an Addressed Admail mailing would typically be between $1.42 and $1.61. However, if the weight exceeds 500 grams (e.g. 501 grams), the piece no longer qualifies for Addressed Admail and would likely be mailed at Parcel Post rates. The Parcel Post rates vary based on destinations within Canada. However, the 501 gram piece would probably cost between $6.00 and $7.00 going out under Parcel Post.