[imp] Mail sent "on behalf of" not searchable.

[Mike Coughlan]

> Sounds like this is entirely due to how you have horde configured to send
> mail - are you using sendmail on the command line?

Thanks again Chuck.  This edit changed our outgoing headers so that mail is
no longer sent
on behalf of www-data.

horde.php
-- $conf['mailer']['type'] = 'sendmail';
++ $conf['mailer']['type'] = 'smtp';