Fastway Couriers, whose parent company entered receivership earlier this week, has said the process to get as many parcels as possible delivered could take up to two weeks.
A spokesperson said just under 50,000 parcels are still in the system, awaiting delivery, down from around 55,000 earlier in the week.
Efforts were made to ensure medical device, perishable goods and a wedding dress were delivered, it said.
It is understood the receivers are still in the process of safely securing parcels from across the network back to Fastway's main hub in Portarlington for redistribution.
The process to get as many as possible of the parcels delivered could take up to two weeks.
Michael Crean who runs a car parts and accessories online shop, MicksGarage, which uses Fastway Couriers as a method of delivery, said that they have 450 parcels currently in the system, due for delivery.
Watch: Are you expecting a delivery from Fastway over the coming days?
"The theory is that we will get a lot of the items back from Fastway," he said.
"But they've also said that it could be 70%, it could be 50%.
"Fastway are telling us it could be next week, it could be the week after."
"But what we are starting to realise is that this could be pushed way out, it could be weeks, it could be months before we see those boxes again," Mr Crean added.
In a statement, Mark Degnan and Brendan O'Reilly of Interpath Advisory who have been appointed as receivers, said: "We understand the significant concern and disruption caused by the receivership of Fastway Couriers and its associated brands, and are working diligently across all areas of the business to manage what is a highly complex situation in an orderly and fair manner."
It added that every effort is being made to ensure that parcels currently held within the network are handled in line with these procedures and that clear information to customers is provided as soon as possible.
"As a priority, we are following the appropriate legal and operational processes to safeguard assets, communicate with clients and support affected employees, contractors and retailers," Interpath Advisory said.
"We appreciate that this situation is frustrating for businesses, customers and staff, particularly given the timing and proximity to the busy trading period, and we ask for patience as we continue to work methodically through the issues to ensure the best possible outcome for all stakeholders," the statement continued.
Read more: 300 jobs under threat as Fastway parent company goes into receivership
