Most letters sent first class locally arrive within one business day. This applies to mail that weighs only 13 ounces or less. Mail sent farther across the nation, or considered non-local, usually arrives within three business days.
When mailing a certified letter, a person should expect it to take from three to five days to reach its destination. Depending on how long it takes the recipient to pick up the letter, the process can take up to 21 days. People who send certified mail receive a notification to prove that the letter has been received by its recipient. When letters are not picked up from the post office, they are returned to the sender marked "unclaimed."