I assume sendmail should be stopped and disabled with 
<code>. /etc/rc.d/rc.sendmail stop
chmod -x /etc/rc.d/rc.sendmail
</code>
before postfix is installed, as postfix has its own sendmail executable to provide functionality for other programs which expect to use sendmail. --- //[[wiki:user:tim|Tim Dickson]] 2015/09/14 14:13//


====== Mistake in the virtual mailbox configuration: ======


To use mysql on a remote server, I had to replace "host" with "hosts" in the virtual mailbox configurations--postfix defaults to 'localhost' anyways, which is why this error goes undetected, but want something besides the default value, and this error must be fixed as thus:  

<code>
emacs /etc/postfix/mysql-virtual-mailbox-domains.cf

# Enter the following lines #
user= mailuser
password = {your mailuser password}
hosts = {mysql server's ip address}
dbname = mailserver
query = SELECT 1 FROM virtual_domains WHERE name='%s'
</code>

(the revision is the "s" that was added to "host") -- slac.in.the.box