Understanding your spam filter result

Understanding your SpamAssassin spam filter result

SpamAssassin is a very popular open source spam filter. Here we are testing against version 3.2, using its default settings.

SpamAssassin scores out of 10. A score of below 6.3 is considered a pass, but it's a good idea to aim for below 3.0.

Some organisations have their threshold as low as 5.0, although they risk losing legitimate email at this level.

Understanding your MessageLabs spam filter result

MessageLabs is an expensive corporate server-side spam filter. It is in use by many large organisations and is very regularly updated.

Somewhat confusingly, MessageLabs score in two different ways. On most emails, MessageLabs will actually report the score from a very well configured SpamAssassin installation, but there is no threshold in this case. So even with a score a 4, the email may be marked as spam.

Sometimes, MessageLabs will process the email using its own filter, which reports a very similar score to SpamAssassin, but rounded to the nearest whole number. In both cases, a score of 3 or more is to be avoided, but Litmus will always report if the email was considered spam by MessageLabs as a separate calculation to the score.

Understanding your Postini spam filter result

Postini is another server-side spam filter, now owned by Google. Like MessageLabs it is in use mainly by large organistions.

Postini offers a 'summary' score between 0 and 100. Unlike the other filters, Postini scores are 'higher the better', with a score of 100 indicating an email is very unlikely to be spam. An email scoring below 1.0 is considered to be spam. Some organisations change this figure, many chose to use 8.0 as a threshold, offering a stricter filter. We have chosen a threshold of 1.0, but you should consider anything under 25 to be a concern.

Postini also rates your email on a number of categories, including 'commercial', 'pornography' and 'racially offensive'. Litmus will report if any of these category matches are triggered. A category score of below 85 is considered notable. If you score above 85, Litmus will hide the category match as scores above 85 indicate that the email is not considered to be of that category.

Understanding your Barracuda spam filter result

Barracuda Spam Firewall is an expensive hardware spam filter that is installed by large organisations within their own datacentres.

Barracuda reports a single score, between 0 and 10 and a flag indicating if the email is considered to be spam. You should be aiming for a score below 3.5.

Please note, for some very spam-like emails, Barracuda will quarantine the email. In these cases Litmus will report the email as considered spam and mark it with a score of 10.0 (the maximum).

Understanding your spam filter results from email clients

Some email clients have built-in bulk email filtering. Where available, Litmus will report if the email was found within this client's spam filter, or if it landed in the inbox as a legitimate email.

Outlook (along with a few other desktop spam filters) utilizes a self-learning filter to determine what you think is spam. While this is great for individual users, it's not consistent nor reliable for use across thousands of tests on our servers. Instead, we've added in hundreds of spam rules that have been published by Outlook. Whenever the content in your campaign triggers one of these rules, we'll provide you with feedback on what can be changed to make your email look less "spammy" to Outlook.

Outlook scores from 0 to 10, with 0 being the highest (passing) and 10 being the lowest (failing).

You may find some email clients report a score of either pass or fail. For email clients, this simply indicates if the email is considered OK (pass) or spam (fail). There are no scores inbetween 0 and 100 for email clients' spam filters.