Virgin Media customers were hit by email problems between Monday and Wednesday, due to a 'cluster failure' on the ISP's Blueyonder platform.
The problems, which lasted from Monday lunchtime to the early hours of Wednesday, were intermittent in nature and did not result in any loss of emails, a spokesperson for Virgin told ZDNet UK on Friday.
"We had a cluster failure on one of our mail platforms," the spokesperson said. "It affected around 100k mailboxes — only those on the Blueyonder platform. [There were] a few delays in accessing email. All email was queued, and the queues are now restored. There wasn't a service outage, just delays or timeouts."
"We believe it was a storage issue — it was working but there was some kind of data flow or queuing issue, but because the fault was intermittent it's a bit hard to pin down."
Virgin Media said in April that it would migrate its customers over to Google Mail. New customers have, since that time, automatically gone onto Google's platform, and the ISP's spokesperson said on Friday that the migration of existing customers is "due to commence in a matter of weeks".