Remove all mail services from ubuntu

List of mail service used for php in ubuntu

1. postfix
2. sendmail
3. mailutils

remove postfix ubuntu

$ sudo apt remove postfix
$ sudo apt purge postfix
$ sudo apt autoremove

remove sendmail service ubuntu

$ sudo apt-get remove sendmail
$ sudo apt-get purge sendmail
OR  To remove send mail completely you have to use:
$ sudo apt-get purge sendmail*

remove mailutils service ubuntu

$ sudo apt-get remove mailutils 
$ sudo apt-get remove --auto-remove mailutils 
$ sudo apt-get purge mailutils 
$ sudo apt-get purge --auto-remove mailutils