We recommend regularly checking your Spam folder for legitimate messages and marking them as “Not spam.” This helps train your filter to better recognize real messages without becoming overly aggressive.

However, sorting through a full Spam folder can be tedious. Below, we explain how to reduce the clutter and quickly spot legitimate emails that may have been misclassified.

How the Runbox spam filter works

The internal Runbox spam filter actually consists of two separate anti-spam systems working together: SpamAssassin, a rule- and signature-based spam filter, and a trainable spam filter and personal spam token database.

The two spam systems work together to scan incoming messages and insert message header tags specifying whether or not they are considered to be spam. Before the messages are delivered to your account, the actual spam filter sorts messages tagged as “spam” to your Spam folder.

Setting up fine-grained spam filtering

Because most spam is caught by SpamAssassin and is very unlikely to be legitimate email, it is possible to set up a manual filter to separate the “SpamAssassin-spam” from the “Dspam-spam” and save the messages most likely to be spam to a separate folder. You can then largely ignore this folder and only scan your “Dspam” folder for possibly misclassified messages. To keep your trainable spam filter up-to-date it’s important that you consistently correct it whenever it makes a mistake.

To set up advanced spam filtering, follow this procedure. Note: Omit the quotes when typing in the input fields.

  1. In Webmail, create a folder called “Spam”, and another one called “Maybe-Spam”.
  2. In Manager:Filter, set your spam filter to save spam to folder “Maybe-Spam”.
  3. In Manager:Filter, create a manual filter with the following parameters:
    Messages where: [Header] [contains] "X-Spam-Flag: YES" will be [saved to folder] "Spam".
    The filter’s priority must be set to “-2” (minus two).

You can now quite safely ignore your “Spam” folder and only scan the “Maybe-Spam” folder for misclassified legitimate email.

Note that your spam filter should be mature before this is attempted, as internal training of the trainable spam filter is bypassed in the above setup. Also, messages caught by Dspam (not by SpamAssassin) will bypass your whitelist.