Suggested improvement for antispam plugin documentation

[Ralph Seichter]

Hello,

I struggled a bit with getting the antispam plugin to work, because the
plugin configuration in http://wiki2.dovecot.org/Plugins/Antispam is
incomplete. After some twiddling, I ended up with this:

  # /etc/dovecot/conf.d/90-plugin.conf
  plugin {
    antispam_backend = mailtrain
    antispam_mail_spam = spam
    antispam_mail_notspam = ham
    antispam_mail_sendmail = /path/to/mailtrain/script
    antispam_spam = Junk;Spam
    antispam_trash = Deleted Messages;Trash
  }

I know that the antispam plugin has not yet been officially released,
but I think it might be worth updating the documentation anyway. Your
thoughts?

-Ralph