Most of them involve changing the daemon’s configuration in /etc/sendmail.mc and rebuilding sendmail.cf
Specific things that can affect performance:
dnl # Sendmail, Chap 24.9.13, Page 955
dnl # Disable re-write of queue control file (will result in duplicates
dnl # if the daemon is interrupted during a delivery)
define(`confCHECKPOINTINTERVAL’,`0′)dnl Read more …
