If you look at an email’s message headers/source, within the spam details you will see something like:
(0.2 points, 2.0 required)
In the above example, 0.2 represents the message’s SPAM score and 2.0 represents your “Tagging Threshold” setting. For this message to have “[SPAM]” in the subject line, it would have to have a score 2.0 or above, and in the example’s case it does not.
In your hosting control panel (cPanel), under the “Email” section if you go to “Spam Filters” you will see “Spam Threshold Score (#)” – any incoming message with a spam score equal to or higher than that value will be tagged as potential [SPAM] but still be delivered. There is also the “Auto-Delete Threshold Score (#)” – any incoming message with a spam score equal to or higher than that value will get outright deleted and will not be delivered. Be very careful if adjusting these values because it can drastically affect how much spam you will receive as well as how many legitimate messages might be marked as spam or even blocked. If you feel the default values are not blocking enough spam or are blocking legitimate messages then we recommend making a small adjustment (less than 2.0 in difference) and then giving it a week of observation to see if that helped. By fine tuning the thresholds in this way you will be able to dial in the level of spam filtering that works best for your company. Keep in mind that while lowering your deletion threshold will reduce the amount of spam you receive, it will also increase the risk of a legitimate message getting blocked. It is much safer to first adjust your tagging threshold and observe the spam scores of any legitimate messages that got tagged as SPAM. This will give you a better idea of a deletion threshold value that should be safe from blocking legitimate messages while preventing as much spam as possible from being delivered.