Yes it does. It is .20 cents more for a square envelope. You can look it up on usps.com. Right now it's .65 cents to mail a square envelope.
The services that the mail offers in the US are certified mail, registered mail, insured mail, express mail, and many more.
The cost of your mail is all about the weight of the package. the more that it weighs, the more it costs. The shape of the envelope is not going to change the price at all
The postage rate to mail a 6x8 envelope in the United States as of 2014 is $0.44 if it is within the regulated weight. Additional costs may occur if it weighs more.
$0.95 if it's a regular envelope; $1.50 if it bends easily and in a larger envelope; $2.12 if it's rigid or more than 1/4 in. thick and in a larger envelope.
The certified mail fee is $2.95 in addition to postage. For example, to mail a one-ounce letter by certified mail with no return receipt, the price is $.45 for postage plus $2.95 for the certified mail fee for a total of $3.40. A return receipt costs extra. For more information about rates, see the Sources and related links section, below.
1 to 2 weeks or more
1 to 14 days or more
"No, the cost of mailing a letter doesn't depend on the shape of the envelope but how much weight is actually inside the envelope. It's based on the weight."
The green arrow on an envelope typically indicates that the mail is being sent as a priority or express service. It signifies that the envelope should be handled with urgency and delivered more quickly than standard mail. This marking helps postal workers identify and prioritize the item during processing and delivery.
1 to 14 days or more
1 to 14 days or more