Letters
Letter-sized mail comprises the bulk of the contents sent through most postal services. These are usually documents printed on A4 (210 x 297 mm), letter-sized (8.5 x 11 inches), or smaller paper and placed in envelopes.
While many things are sent through the mail, interpersonal letters are often thought of first in reference to postal systems. Handwritten correspondence, while once a major means of communications between distant people, is now used less frequently due to the advent of more immediate means of communication, such as the telephone or e-mail. Traditional letters, however, are often considered to harken back to a "simpler time" and are still used when someone wishes to be deliberate and thoughtful about their communication.
Bills and invoices are often sent through the mail, like regular billing correspondence from utility companies and other service providers. These letters often contain a self-addressed, envelope that allows the receiver to remit payment back to the company easily. While still very common, many people now opt to use online bill payment services, which eliminate the need to receive bills through the mail.
Bulk mail, often called junk mail, are commercial solicitations sent by advertisers. The senders of these messages sometimes purchase lists of addresses (which are sometimes targeted towards certain demographics) and then send letters advertising their product or service to all recipients. Other times, commercial solicitations are sent by local companies advertising local products, like a restaurant delivery service advertising to their delivery area or a retail store sending their weekly advertising circular to a general area. Bulk mail is also often sent to companies' existing subscriber bases, advertising new products or services.
Many other things are also sent as letters through postal services, like wedding invitations and bank statements.
Postcards
Postcards are small message cards which are sent by mail unenveloped. The original postcards were plain and had the postal service's name on them. More commonly today postcards are for tourism, with pictures of resorts, tourist attractions or humorous messages on the front and allowing for a short message from the sender to be written on the back. The postage required for postcards is generally less than postage required for standard letters.
Postcards are also used by magazines for new subscriptions. Inside many magazines are postage-paid subscription cards that a reader can fill out and mail back to the publishing company to be billed for a subscription to the magazine. In this fashion, magazines also use postcards for other purposes, including reader surveys, contests or information requests.
Other
Larger envelopes are also sent through the mail. These are often made of sturdier material than standard envelopes and are often used by businesses to transport documents that are not to be folded or damaged, such as legal documents and contracts. Due to their size, larger envelopes are sometimes charged additional postage.
Packages are often sent through some postal services, usually requiring additional postage than an average letter or postcard. Many postal services have limits on what can and cannot be sent inside packages, usually placing limits or bans on perishable, hazardous or flammable materials. Additionally, because of terrorism concerns, the U.S. Postal Service subjects their packages to various security tests, often scanning or x-raying packages for materials that might be found in mail bombs.
Magazine subscriptions are also sent through postal services. Many magazines are simply placed in
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