1. Set your authorization informations by putting the following line to /etc/mail/authinfo file:

AuthInfo:outbound.mailhop.org "U:USERNAME" "P:PASSWORD" "M:PLAIN"

 Note: Replace USERNAME and PASSWORD with the mail relay username and PASSWORD.

2. Add following lines to /etc/mail/sendmail.mc (check if apropriate settings doesn't already exists):

define(`SMART_HOST', `outbound.mailhop.org')  

FEATURE(`authinfo')

3. Update sendmail.cf and access.db files:   

# cd /etc/mail  

# m4 sendmail.mc >sendmail.cf  

# makemap hash authinfo < authinfo 

4. Reload or restart sendmail:  

# /etc/init.d/sendmail restart

For any version of Sendmail

1. Set your authorization informations by adding following line to /etc/mail/access file:

AuthInfo:outbound.mailhop.org "U:USERNAME" "P:PASSWORD" "M:PLAIN"

   Note: Replace USERNAME and PASSWORD with the mail relay username and PASSWORD.

2. Add following lines to /etc/mail/sendmail.mc (check if apropriate settings doesn't already exists):

define(`SMART_HOST', `outbound.mailhop.org')  

FEATURE(`access_db')

3. Update sendmail.cf and access.db files:   

# cd /etc/mail  

# m4 sendmail.mc >sendmail.cf  

# makemap hash access <access 

4. Reload or restart sendmail:  

# /etc/init.d/sendmail restart

Note: If it does not work, you need to make sure the saslauthd is running on the server. saslauthd is the daemon for sending authentication . You may issue "service saslauthd start" to start the service.