the mail guard feature provides safe access for simple mail transfer protocol (smtp) connections from the outside to an inside messaging server. this feature allows a single mail server to be deployed within the internal network without it being exposed to known security problems with some smtp server implementations. avoids the need for an external mail relay (or bastion host) system. mail guard enforces a safe minimal set of smtp commands to avoid an smtp server system from being compromised. this feature also logs all smtp connections.