Broadband internet customers using social networking website Friends Reunited could have a large number of their email messages blocked by internet service providers (ISP).

At one point, broadband bundle providers were blocking as many as one in four emails generated by the website. Of those that did make it through, a further 5.7 per cent were ending up in people's junk folders.

However, according to ISPreview.co.uk, Friends Reunited, which offers the chance for old school friends to reconnect with each other after their academic careers have run their course, has managed to reduce the number of messages that end up being blocked by broadband providers as spam.

The firm has worked closely with Return Path to boost email deliverability from 67.1 per cent in May to 92.5 per cent in June 2010.

Duncan Careless, Friends Reunited's chief technical officer, said: "As a social network, the deliverability of email is imperative to staying in touch with our users, growing our subscriber base, but more importantly to keep our users in contact with each other.

"Return Path's deliverability monitoring suite enables us to monitor our email reputation."

According to Return Path, millions of legitimate emails are blocked by ISP's spam filters every day.