A public web server must limit email to outbound only.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-2261	WG330	WG330 A22	SV-32937r1_rule	2019-01-07	1

Description
Incoming E-mail has been known to provide hackers with access to servers. Disabling the incoming mail service prevents this type of attacks. Additionally, Email represents the main use of the Internet. It is specialized application that requires the dedication of server resources. To combine this type of transaction processing function with the file serving role of the web server creates an inherent conflict. Supporting mail services on a web server opens the server to the risk of abuse as an email relay.

Description

Incoming E-mail has been known to provide hackers with access to servers. Disabling the incoming mail service prevents this type of attacks. Additionally, Email represents the main use of the Internet. It is specialized application that requires the dedication of server resources. To combine this type of transaction processing function with the file serving role of the web server creates an inherent conflict. Supporting mail services on a web server opens the server to the risk of abuse as an email relay.

ℹ️ Check
"To determine if email applications are excepting incoming connections (on standard ports)enter the following command: telnet localhost 25 review the command results, If an e-mail program is installed and that program has been configured to accept inbound email, this is a finding."

✔️ Fix
Configure the email application to not allow incoming connections.