Complete removal of postfix, SpamAssassin and Dovecot in Ubuntu

You will not have time to be attached to any pleasant, calm place, and already some voice makes you stand up and retire from it, as the hour of rest has passed.
–Charlotte Bronte. Jane Eyre–Edward Rochester

In case you need to reinstall postfix, spamassassin and dovecot in ubuntu, first remove:

apt-get --purge remove postfix postfix-mysql spamassassin dovecot-core dovecot-common dovecot-imapd dovecot-pop3d