Step 1: apt-get install sendmail
Step 2: /etc/init.d/apache2 restart

> apt-get install ssmtp
> Configured "/etc/ssmtp/ssmtp.conf" file.

root=notifications@fostergen.com
mailhub=smtp.fostergen.com:587 (Here I have doubt. I am not sure what to use here. I tried smtp.fostergen.com:587, smtp.fostergen.com:25,mx1.mailhostbox.com :587,mx1.mailhostbox.com:25.

FromLineOverride=YES
UseSTARTTLS=YES
AuthUser=notifications@fostergen.com
AuthPass=password provided during email registration on bigrock

> edited /etc/ssmtp/revaliases
(added " root:notifications@fostergen.com:mx1.mailhostbox.com :587 " in the last line)
> edited php.ini file (sendmail_path = /usr/sbin/ssmtp -t)
> /etc/init.d/apache2 restart

> apt-get install esmtp
> edited /etc/esmtprc
    hostname=smtp.fostergen.com:587
   username= notifications@fostergen.com
   password: password provide by bigrock
    mda="/usr/bin/procmail -d %T"
> linked eSMTP to the legacy Sendmail path by execting the command "ln -s /usr/bin/esmtp /usr/bin/sendmail"
> edited php.ini file (/usr/bin/sendmail -t -i)
> /etc/init.d/apache2 restart