From this month to the end of the year, a little-known five-member team at Singapore Post will be working doubly hard to match "lost" mail with its rightful owners.
On average, 4,000 pieces of mail end up with the Returned Letters Unit every day, but this number goes up to about 6,000 during the last three months of the year.
The increase is due to letters being sent out during the festive season, including some 500 which are addressed to Santa Claus every year.
"We post them out of goodwill," said Mr James Cheong, operations manager of SingPost's mail processing department, which oversees the unit in Paya Lebar. "We do not want to let our customers, especially young kids, down," he said, adding that these letters are sent to Santa's "offices" in Alaska in the United States or Finland.
Letters are also written to God and North Korean leader Kim Jong Un. But as their whereabouts are unclear, it is tough for letter writers to give valid addresses. This makes it tough for the Returned Letters Unit to send these on too.
More recently, the unit - housed in the SingPost mail processing facility in Paya Lebar - has also received mail for Singapore's President Halimah Yacob.
The unit keeps a newspaper cut-out which shows all office holders and their current designations, as many letters addressed to politicians arrive without addresses.
"We have to be up to date on their current roles, so that we can send these letters to their official work addresses," Mr Cheong said.
Invalid or blank addresses, however, are the least of their worries.
Many times, the "mail" that's put in the postbox is not actually mail.
The unit gets items that cannot be delivered, including inflated balloons, bananas, underwear and even packets of nasi lemak - all with stamps and written addresses.
Common items that the unit does deal with are identity cards and passports. In fact, it gets more than 160 identity cards and over 30 passports every month.
"The postbox is just like a lost and found box," said Mr Cheong. "People will just throw these items in."
WHEN IT'S NOT ACTUALLY MAIL
The postbox is just like a lost and found box. People will just throw these items in.
MR JAMES CHEONG, operations manager of SingPost's mail processing department, which oversees the Returned Letters Unit in Paya Lebar, on items such as identity cards and passports that the unit gets.
Many of the mail items that pass through the unit are letters and packages with no stamps, illegible handwriting, incomplete addresses or addressed to places that no longer exist. Mail that cannot be returned is normally kept in a vertical lift storage system. Registered mail items are classified by their registered numbers, while others are arranged by the month received to make searching easier.
When customers approach SingPost about a missing letter or package, the unit tries to find out as many details as possible, such as its size and the date it was posted, before scouring through the pile for it.
Even with the machine, work at the unit is largely manual. The team also spends a lot of time tracing and translating addresses which are not written in English, relying on dictionaries and old street directories.
Despite their hard work, only about 300 mail items are eventually traced and returned, out of the 4,000 they receive daily.
Due to the large volume that they receive and the limited space that they have, ordinary mail is kept for three months, while registered mail is stored for six months. After that, the letters are incinerated. To maintain privacy, none of the letters is ever opened. But unclaimed packages are opened and usable items are donated to charities.
To ensure that senders get their mail delivered, they should write complete addresses legibly, with valid return addresses should they go undelivered, Mr Cheong urged.
"We feel a sense of satisfaction when we finally get these mail delivered, because they might be important to those who send or receive them," he said.