Posted by Virus Bulletin on Jan 26, 2010
Less than five per cent of all SMTP connections result in an email being delivered into a user's inbox.
A survey carried out by the European Network and Information Security Agency (ENISA) among 92 internet and telecom providers suggests that less than five per cent of all SMTP connections result in an email being delivered into a user's inbox.
The survey - the respondents to which represented over 70 million inboxes in 30 countries - showed that just over 15% of all SMTP connections are accepted in the first place, with blacklisting by far the most popular method of aborting connections. Of the accepted connections, almost 80% are filtered out as either spam or virus-infected.
Apart from blacklisting and content filtering, greylisting, sender authentication and URI blacklisting are the most popular anti-spam measures, though interestingly they are less popular among the largest providers; those are more likely to use a reputation system. Just short of 40% of providers use SPF to authenticate the sender, while less than 20% use DKIM.
The report also revealed that almost all providers use some kind of spam filtering, usually on the network level, which is generally free of charge. Some providers also offer desktop anti-spam solutions, although these are less likely to be free.
Spam filtering isn't just used to take some pressure off the networks: according to the report, most providers believe that having a good anti-spam solution is a competitive advantage and that potential customers take this into account when selecting their provider. It is not surprising, then, that a third of the largest providers spend over one million euros annually on anti-spam measures.