The Royal Mail has failed to shed further light on the reasons behind the problems customers are experiencing when trying to buy online postage, saying only that "technical issues" are to blame.

The latest bout of problems started at the weekend and are still affecting operations today on the Capgemini-managed Royal Mail website. This is the fifth consecutive month that users have experienced problems trying to access the Royal Mail's SmartStamp and online postage service since online data was migrated to new servers in December 2011.

A Royal Mail spokesperson said that the problems do not affect the purchase of stamps from its online shop, but a message posted by the company on its Twitter feed at 16:05 GMT today apologised again for 'OBA (Online Business Account) & SmartStamp' still being unavailable.

"We are sorry that technical issues mean that some customers are experiencing difficulties accessing the Online Postage application on Royal Mail's website," the Royal Mail spokesperson said.

"We do very much appreciate the inconvenience this is causing some Online Postage customers. We are working hard to resolve the issues as quickly as possible.

"We will keep customers updated on our progress as we strive to restore service to normal."

Owen Cole, VP of EMEA at ExtraHop Networks, suggested that the Royal Mail's problems are being caused by a network or application issue.

"If these are only being monitored on a reactive basis, then issues will only arise when customer-facing applications fail. Businesses need to be able to see, predict and fix issues in real time to prevent issues before they occur.

He also believes that Royal Mail's repeated website failures should act as a warning sign to all businesses.

"As the Royal Mail is now discovering, the costs of not proactively monitoring the performance of systems can be substantial. Not only can this impact businesses' revenue, but customers are unlikely to forget any disruption to services."