Microsoft Exchange 5.5 allows a remote attacker to relay email (i.e. spam) using encapsulated SMTP addresses, even if the anti-relaying features are enabled.Referenceshttp://support.microsoft.com/default.aspx?scid=kb%3B%5BLN%5D%3BQ237927http://www.ciac.org/ciac/bulletins/j-056.shtmlhttp://www.securityfocus.com/bid/567https://docs.microsoft.com/en-us/security-updates/securitybulletins/1999/ms99-027
