Use your ISP with Sendmail

# cp /usr/share/sendmail/cf/cf/sendmail-frugalware.mc /etc/mail/sendmail.mc

# nano /etc/mail/sendmail.mc

Add this :

this line should be add Before MAILER(XX) :

FEATURE(`authinfo',`hash /etc/mail/authinfo.db')

MASQUERADE_AS(`yourISP.domain')dnl

MASQUERADE_DOMAIN(`youractual.domain')dnl

FEATURE(masquerade_entire_domain)dnl

FEATURE(masquerade_envelope)dnl

define(`SMART_HOST',`[NameSmtpServer]')

This line just for have debug when all works 

define(`confLOG_LEVEL', `20')dnl 

Generate sendmail.cf: 

# cd /usr/share/sendmail/cf/m4

# m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf

Configure the identification :

# nano /etc/mail/authinfo

AuthInfo:NameSmtpServer "R:NameDomain" "U:Login" "P:Password" "M:PLAIN"

Generate the db :

# /usr/sbin/makemap hash /etc/mail/authinfo < /etc/mail/

Configure Sasl :

# nano /etc/sasl2/Sendmail.conf

pwcheck_method: saslauthd

mech_list: login plain

Start Sendmail :

# /usr/sbin/sendmail -bd -q1h

Stop Sendmail

# killall sendmail

PS :

For use it with apache, the user that you use for apache (for me it's nobody) should have the permission to write into /var/spool/clientmqueue/