This value determines the "spammy-ness" level at which mail will be tagged as spam. Spam scanning assigns spam levels to tested email. If the spam score of an email matches or exceeds this value, then the mail will be considered spam.

Higher values make the scanner less sensitive (i.e. less mail will be considered spam) and risks having spam slip through untagged.

A lower value, on the other hand, makes the scanner more sensitive (i.e. more mail will be considered spam), but risks having non-spam falsely tagged as spam (i.e. there's a greater chance of false positives).

A value of 5 is average, and the default value. A cautious organization might choose a value of 7, and an organization which gets a lot of spam might set this to 4.

A value of less than 4 is not recommended unless your organization is closely monitoring your spam trap(s) to spot false positives and are extensively whitelisting the email addresses or domains of those with whom you have common contact.

Organizations should monitor their incoming spam for false positives, or legitimate mail that was wrongly tagged as spam.

However, while it's possible that an email with a score of 5 is a false positive, and vaguely conceivable that an email with a score of 7 is a false positive, the odds of a high scoring email being a false positive are practically nil. Therefore, there is little point in monitoring high scoring spam for false positives.

Setting this value will cause mail scoring above this level to be simply deleted, and not be delivered.

A value of 12 is average. A value of 15 is cautious and a value of 10 is aggressive.

Setting this less than 10 is not recommended.

Depending on the spam your organization receives and the level you select, half to three quarters of spam is high-scoring.

PLEASE NOTE: mail automatically deleted this way is completely non-recoverable. Because of this, it is suggested you do not use this feature until you have monitored your spam for a while and are confident that you do not receive any high-scoring false positives.

If filled in, this will have the contents of this box prepended to the Subject line of all detected spam messages.

e.g.

Subject: Buy this now!!!!

becomes

Subject: *SPAM* Buy this now!!!!

This is useful for visually separating spam from non-spam, and can also easily be used by a mail filter or mail rule in users' email clients as a trigger to move mail from users' Inboxes to a separate Spam folder.

One of the goals of spam scanning is not just to tag the spam, but to also remove the spam from users' Inboxes.

This can be done either client-side or server- side. For client-side, each mail client must have a mail filter or mail rule implemented that moves mail that has been tagged as spam from the Inbox to a separate Spam folder (i.e. a spamtrap). For large or non-technically inclined organizations, this may be impractical.

In addition, it is likely that a large portion of your user base will ignore their spamtrap and never review it for false positives.

With server-side filtering, all mail that has been tagged as spam is re-routed from the intended recipient to an organization-wide spamtrap. This global spamtrap is set up on your mail server as an ordinary email account except that all it will receive is your organization's spam.

One person is then designated to review the spam caught in the spamtrap for false positives. If any are found, this person may then forward the mail to its original recipient (the original recipients are recorded in every message's headers).

It's unglamourous, but with practice takes little time and provides excellent protection from false positives so you can be more agressive with your tagging score. Ideally, this person would also enter the sending address of any false positive into your domain's whitelist via this webpage.