Hide SMTP flag (Sendmail/qmail/postfix/exim)

Hiding the flag (software name and version number) will improve security and, if possible, use a mail server other than SendMail because SendMail runs as root, making it easier to raise the hacker to root.

　　Sendmail

Look for SendMail's configuration file and edit:

Code: Locate SENDMAIL.CF Nano-w/path/to/sendmail.cf

Modify the bold portion of the following code:

Code: smtpgreetingmessage= $j Sendmail $v/$Z; $b

Restart SendMail or overload its configuration file (Killall-hup sendmail).

Qmail

Modify the smtpgreeting value of the QMAIL-SMTPD, for example:

Code: mail.example.com Greetings here

Postfix

Look for Postfix's configuration file and edit:

Code: Locate MAIN.CF Nano-w/path/to/main.cf

Modify the bold portion of the following code:

Code: Smtpd_banner = $myhostname ESMTP $mail _name ($mail _version)

Restart Postfix.

　　 EximExim is similar to postfix, modifying the Smtpd_banner variable in/etc/exim.conf.