HP-UX Mailing Services Administrator's Guide

Configuring and Administering Sendmail
Security
Chapter 280
Disabling identd from the Sendmail Server
This is probably an easier way of disabling identd, because you need not
be concerned about the remote client having identd disabled. In the file
/etc/mail/sendmail.cf on the Sendmail server, modify the following
entry:
#O Timeout.ident=5s
as
O Timeout.ident=0s
Now, you need to kill and restart Sendmail.