If you are interested in one of these positions, you can explore this type of work by seeking part-time work during vacations and summer periods, especially the rush holiday periods when many more jobs become available. Related jobs such as store or office clerk, stock clerk, shipping clerk, or others that require sorting and distributing materials or dealing with the public, might also be beneficial when looking for a position in this area.

Postal clerks may perform numerous duties. Those who work in large city post offices, however, usually perform more specialized tasks as either postal window clerks or distribution clerks. In small post offices, clerks may perform both types of work, sorting mail for distribution when business at the customer windows is slow. Wherever they are employed, all postal clerks must know how to sort mail.

Window clerks deal directly with the public at the post office service windows. They sell stamps, accept and weigh parcel post packages, and advise customers regarding parcel post regulations and foreign mail postal fees. They also sell and cash money orders, register mail, rent post office boxes, accept deposits for postal savings accounts, and sell U.S. Savings Bonds. When customers come to the post office to pick up a special package or letter, postal clerks examine the customers notices and retrieve the items. In addition, they may answer customer questions about postal rates and rules.

In large city post offices, postal window clerks may specialize in only one or two of these services, such as working a window for money orders, savings bonds, and registered mail only, or working at a window at which only stamps are sold and parcel post accepted. Still other clerks may work general delivery windows. Service agents at Federal Express and administrative assistants and account executives at UPS offer customers assistance and follow up on complaints. Service agents, like postal clerks, also handle packages, so they must do some heavy lifting.

Distribution clerks begin their work when the carriers and delivery drivers who have collected mail bring it back to the post office. The mail from route boxes and mail carriers bags is dumped onto long worktables. Usually, the new distribution clerks, also known as mail handlers, perform the first rough separation of the mail into parcel post, paper mail, and letter mail. The mail is then "faced" (placed with stamps down and facing the same direction) so that it can be fed into canceling machines. These machines mark each piece of mail with the date, time, and the city and state in which the post office is located. Once the mail is canceled, it is moved to different work sections where distribution clerks sort the mail according to its destination.

Clerks operating electronic letter-sorting machines push keys corresponding to the zip code of the local post office to which each letter will be delivered. The machine then sends the letter to the proper slot or bin. A growing number of clerks operate optical character readers (OCRs) and bar code sorters, which are machines that can "read" the address and sort a letter according to a code printed on the envelope. According to the USPS, barcodes are now on the majority of letter mail. Other clerks sort odd-sized letters, magazines, and newspapers by hand. Finally, the mail is sent to local post offices for sorting according to delivery route.

Parcel post sorting is performed in a similar manner using conveyor belts, slides, and chutes. These packages require even finer separating and routing before they are sent to local post offices to be delivered by the mail carrier.

Mail clerks in the mailrooms of business firms perform duties similar to those described above. With the rise of private mail delivery services, mail clerks are also employed by letter and package delivery services. They take payment, label packages, assist customers in packing, and route mail to the delivery system.

All distribution clerks must be able to perform their duties accurately and efficiently so that the mail may be transported to its correct destination as soon as possible. A related occupation includes transfer clerks, who are responsible for moving the mail being carried to and from train stations and airports with the greatest speed possible.