An email approval ratio can be set on both the mail inbox and the mail's inbound mail rules. This introduces possible ambiguity on which approval ratio is the effective one. The higher of the two values is always taken as the effective approval ratio. For example, if a mail arrives through a mailbox where the approval ratio is 50%, and on a rule where the approval ratio is 0%, then the effective email approval ratio for that mail is 50%. That is 50% of mail arriving through that mailbox and rule is marked for approval.