New guidelines could encourage broadband providers to help customers fight spam sent to their email addresses, according to new reports.

Recommendations from the Messaging Anti-Abuse Working Group (MAAWG) suggest that ISPs use separate servers for received and forwarded e-mails, as well as blocking port 25, through which spam mail travels through.

Although experts say that the move may not drive down the volume of spam received by customers by a significant amount, action by broadband providers could help prevent volumes rising.

Matt Sergeant, security firm MessageLabs' senior anti-spam technologist, commented: "Some ISPs will always remain wide open even if we succeed in closing port 25."

"But that doesn't mean that it isn't worth doing. If we don't do it spam volumes will increase."

The issue is due to be debated in September at the MAAWG's annual general meeting in Florida.