SingPost has apologised to customers for its recent service failures, which it said were due to a "tremendously busy" peak season in November and December that was "beyond forecasts".
Due to an increase in the volume of packages, its postmen had to make an extra 20 doorstep deliveries on average daily, as well as work beyond their usual hours, SingPost said in a Facebook post on Monday.
"We hired extra resources, recalled personnel and activated teams from the corporate office on Saturdays just to meet the demand, but our service quality still suffered as a result," it said.
Social media users have in recent weeks been vocal about what they claimed was poor delivery service by SingPost.
Facebook user Andy Lau, whose Dec 26 post went viral, said a delivery man left a note on his doorstep and ran off after knocking on his door for a few seconds.
Mr Lau added that he confronted the delivery man, who seemed unable to explain his actions.
His post led to other social media users sharing similar experiences.
SingPost, in its Facebook posting, said that, being part of the service industry, it is dependent on front-line staff to provide the best experiences for customers, though "inevitably, there will be employees who may not act in the best interests of the company".
It added: "We have experienced service failures due to the individual actions of a few employees. We are aware that this not only reflects badly on our organisation, but also undermines the hard work, commitment and dedication that the majority of our postal staff are displaying every single day.
"Such behaviour will not be tolerated."
In apologising to customers, SingPost also said it is taking a serious look at the issues that have surfaced in recent weeks and will find ways to improve immediately.
The company processes an average of three million mail items daily.
"We assure you that we will be vigorous in reviewing and revising our operational procedures, so that you will receive your letters, packages and parcels without delay, without hassle and, most importantly, without frustration," SingPost added.
Some netizens are still unhappy despite the apology, leaving complaints on SingPost's Facebook page.
Facebook user Jesse Cheong, for example, claimed that a postman had forged her signature on a delivery notice a while ago and left the item in her letterbox without her knowledge.
But there are also netizens who are sympathetic. Facebook user Selina Wee said: "It's tough on SingPost when there are so many online purchases nowadays. Be more understanding."