скрыть версию сендмыла

$ grep Greet /etc/mail/sendmail.cf
O SmtpGreetingMessage=$j Server (Microsoft Exchange Internet Mail Service 5.5.2653.13) ready
$ telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 localhost ESMTP Server (Microsoft Exchange Internet Mail Service 5.5.2653.13) ready
help
214-2.0.0 Commands:
214-2.0.0 HELO EHLO MAIL RCPT DATA
214-2.0.0 RSET NOOP QUIT HELP VRFY
214-2.0.0 EXPN VERB ETRN DSN AUTH
214-2.0.0 STARTTLS
214-2.0.0 For more info use "HELP <command>".
214-2.0.0 For local information send email to Postmaster at your site.
214 2.0.0 End of HELP info

Ну хорошо...

[root@host /]# grep Greet /etc/mail/sendmail.cf
#O SmtpGreetingMessage=$j Sendmail $v/$Z; $b
O SmtpGreetingMessage=$j Server (Microsoft Exchange Internet Mail Service 5.5.2653.13) ready
[root@host /]# telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.host.
Escape character is '^]'.
220 host.ru ESMTP Server (Microsoft Exchange Internet Mail Service 5.5.2653.13) ready
help
502 5.3.0 Sendmail 8.12.6 -- HELP not implemented

и?

ну значит у тебя патченый sendmail, либо возми нормальный c sendmail.org либо правь сырцы :-)

Там файлик есть такой /etc/mail/helpfile
содеожит строку "smtp This is sendmail version $v", смени, например на "smtp This is ESMTP Server (Microsoft Exchange Internet Mail Service 5.5.2653.13)"