Royal Mail has confirmed that it is still suffering from website glitches that began more than a month ago following a migration of online data to new servers.
The issues caused some customers to be overcharged, and many services, such as the Royal Mail SmartStamp and Online Postage applications, were knocked offline over the busy Christmas period.
A spokesperson for the company said that all applications on the Capgemini-managed website are now available, except for the Pricefinder service.
"Royal Mail is sorry that the recent issues with some parts of our website are still affecting a small number of users of our SmartStamp and Online Postage applications.
"We are continuing to investigate the causes of these issues to identify solutions for individual customers, wherever possible," said Nick Martens, Royal Mail spokesperson.
Royal Mail said that it was working "closely" with Capgemini to resolve the issues.
It added that it has finished crediting all customers who were charged twice for the SmartStamp service, and made an additional "goodwill" payment of £25 to those affected.