Each marking rule has a priority level, which you assign when you create it. When the rule with the highest priority marks an item, no rule with a lower priority can mark the same item. Even if the conditions on the rule with the lower priority value would match the item, it is excluded from automatic categorization under this rule.
Rules that you have configured to apply both marks and tags to items also have a priority level. After a rule that applies both marks and tags has automatically categorized items, these items cannot be categorized by lower priority rules.
To change the priority level of a marking rule