The study – billed as the first of its type – and carried out by Osterman Research with sponsorship from Commtouch, reveals 68% of ISPs are being hit by an annual tab of more than $100 000 for the problem.
Osterman Research says that the exploitation of service providers' networks to send unsolicited email can lead to customer loss, operational cost increases, brand damage and even potential lawsuits.
Michael Osterman, the firm's president, said that the results of the research pin-point a growing challenge in the industry that service providers need to protect against spammers who aim to abuse their networks.
"Outbound spam is a rising concern, and it is essential that service providers deal with the issue in order to protect their businesses", he said.
Four percent of ISPs say the issue of spam being generated on their networks is costing them in excess of $250 000 a year.
Costs due to outbound spam, says Osterman Research, include such things as IT helpdesk and anti-abuse team time.
But it gets worse, as almost 40% of respondents have had their IP addresses listed on Real Time Blackhole Lists (RBLs) in the past 12 months alone.
It's not all doom and gloom, however, as nearly 70% of service providers are in the process of evaluating solutions for their outbound spam problem. Half, meanwhile, expect to deploy a solution within the next 12 months.