Envelope Sender override (RP_MATCHES_RCVD rule) This option is available through menu Anti Spam > Setup. By default the Anti Spam filter checks whether the domain name of an envelope sender address matches the domain name of the first untrusted relay server (if any), or any trusted relay otherwise. If the match is positive, the mail is unlikely to be spam. However, in some cases spammers may use this feature to bypass the Anti Spam filters, therefore you may prefer to override this check. The Envelope Sender check is active by default. To override it, you should check the check box . As a consequence, the Protector will assign a score of zero to the rule RP_MATCHES_RCVD. The only warning is that when this option is enabled, the check is ineffective and risk of false positives grows (valid mail marked as spam).