Business and consumers across the UK are still facing worries that Christmas deliveries won't arrive on time.
"Some things haven't been delivered yet, and it's causing stress to people waiting," said Ellie Chalkley, who has an Etsy shop in Glasgow.
With just a week till the festive celebration, couriers are dealing with an unprecedented volume of parcels.
"All delivery companies are experiencing exceptionally high volumes this year," said the Royal Mail.
It added that the majority of the Royal Mail network is now running as usual in line with the seasonal peak in demand.
Problems have grown because of a huge increase in online Christmas shopping, partly driven by the recent lockdown, and the ongoing Covid restrictions.
According to the online retail trade body the IMRG, sales for the first two weeks of December jumped by just over 50% compared to the previous year.
"We could not possibly have anticipated this level of packets and parcels, it seems to be intensifying every day," said Terry Pullinger, deputy general secretary of the Communication Workers Union.
"That coupled with the arrangements that are going to be in place to keep key workers safe because of COVID and the rising spread of COVID, is complicating what is already a strategical nightmare."
A week late
"Anything that is sent to me via Royal Mail is arriving at least a week late," writer Geordie Clarke who lives in north London told the BBC.
"For the past six weeks I've had one postal delivery every week to 10 days for letters and cards, and parcels arrive whenever.
"For example, it took nine days for a 48-hour tracked parcel to arrive."
But financial adviser Andy Rainer, who lives in the Scottish Highlands, reported the opposite experience.
"We haven't experienced any problems, although we may be the lucky ones," he told the BBC.
"Parcels sent on Wednesday arrived yesterday. Christmas cards have been sent and received the following day."
The Royal Mail took on around 33,000 seasonal workers to help it cope with the increased demand as well as opening two extra temporary sorting centres.
Even so, some Royal Mail sorting offices and delivery depots fell behind, resulting in delays for customers.
"From the start, we have always said that despite our best endeavours, it is possible that some areas of the country may experience a reduction in service levels due to COVID-related absences and necessary social distancing measures at local mail centres and delivery offices," it said.
Last delivery dates
Friday 18 December is the last recommended posting date for second class letters and packages, although there's no guarantee they will reach their destination on time.
Monday 21 December is the last recommended posting date for first class deliveries although, again, there's no guarantee of timely delivery.
Wednesday 23 December is the last chance to use Royal Mail's Special Delivery Guaranteed by 1pm the next day service in time for Christmas.
It costs from £6.70 for a 100g letter, rising to £41.20 for a 20kg parcel.
Royal Mail - along with other couriers - offers a tracking service so you can follow the progress of your package.
Mariusz Luczakowski runs a small chocolate company in Worcestershire and uses Royal Mail to send out orders to customers via first class delivery. Over the past few days he says he has received emails from customers complaining of delays - sometimes of seven or more days.
"I am feeling frustration, but at least it's not only me," he told the BBC.
"It is a really scary and uncertain time for a small business owner and so easy to destroy the reputation of your own company by not delivering on time as promised."