Sunnie Smith grew tired of waiting five days for her mail to reach its destination.
In Craig, mail is shipped to Glenwood Springs for automated processing -- even if it's only going from one Craig address to another.
"It was getting to be a pain, because I would send something and they didn't get it, didn't get it, didn't get it," Smith said.
So she set out to learn a little about how the mail gets moved. And she discovered a simple, if little-known trick to reduce delivery times: the four-digit suffix.
Most businesses already use the ZIP+4 system, but many residents are unaware that it can be used by anyone, said Don Offutt, acting manager of the Craig Post Office.
Smith tried an experiment. She sent two letters to herself -- one with the ZIP+4 digits and one without. The letter with the four digits arrived a day after she mailed it. The other letter took five days.
According to the Postal Service's customer service office, addressing envelopes with the correct ZIP code and four-digit suffix reduces the amount of handling and decreases the chances for shipping errors.
Offutt said he didn't know how much time could be saved by including the four-digit ZIP code. The mail is electronically scanned in Glenwood Springs. If the four-digit ZIP+4 code is included, the machine sorts it. Otherwise, the suffix needs to be looked up and the number needs to be printed on the item.
People can learn their four-digit ZIP code suffix by calling 1-800-ASK-USPS.
"I wouldn't say there's a lot of people that think about those last four digits," Offutt said.