[Dovecot] pop for one ip spop for another

[arjan]

Dear Timo,

Thanx for your reply. But I can't immediately act on your answer.

> > Is it possible to enable pop only for a specific ip and enable spop for
> > every other ip?
> > I've a vserver in which an application can check mail via pop, but not
> > spop. And I don't like to enable pop for the outside world. 
> 
> a) Firewall. Probably a better idea.
Yes, I will request to disable the ports 110 and 143 in the firewall,
but since we don't manage the firewall ourselves, I would also be able
to configure this in Dovecot.

> b) Fail authentication if non-secure authentication comes from outside
> world. 
Clear, that's what I would like. But how? How do I differentiate? How
can I say if this, then that? 

I'm using passwd:
auth_userdb = passwd
auth_passdb = pam

Do I do something within
protocol pop3 {

}
But how can I make an if/then-like statement so that I can use:
> If you're using SQL as passdb this would be easy. With anything
> else probably not. %r and %c variables anyway allow this
> (http://wiki.dovecot.org/Variables)

It's not possible to do this I've discovered:
protocols = pop3 pop3s
disable_plaintext_auth = yes
(...)
userdb static {
    args = uid=1005 gid=1005 allow_all_users=yes
disable_plaintext_auth=no
  }

Here I tried to make siable_plaintext_auth different for a specific
user.

Kind regards,
Arjan.