dovecot - Jan 2011 - enforce STARTTLS on port 110 with POP3?

Hi there, 

We are using DoveCot 1.0.7. User will use POP3 or POP. We want to force
user to securely send their credential and keep a secure connection
between us and them. We can do TLS/SSL on port 995, or STARTTLS on port
110. 

The problem is that we have no way to enforce STARTTLS on 110, user can
connect to DoveCot on port 110, sending user credential without STARTTLS
(thus insecure). 

Reading DoveCot documentation does not sound it supports this. Here is
what I got from documentation.  Dovecot supports:

    * IMAP (including TLS/STARTTLS)
    * IMAP+SSL ("imaps")
    * POP3 (including TLS/STLS)
    * POP3+SSL ("pops")

My only option to enforce securely sending user credential is to enable
port 995 and disable port 110, sound right?

Thanks,
 Yan






Confidentiality Notice: The information contained in this electronic
transmission is confidential and may be legally privileged. It is intended only
for the addressee(s) named above. If you are not an intended recipient, be aware
that any disclosure, copying, distribution or use of the information contained
in this transmission is prohibited and may be unlawful. If you have received
this transmission in error, please notify us by telephone (513) 229-5500 or by
email (postmaster at MedPlus.com). After replying, please erase it from your
computer system.

On 10.1.2011, at 23.09, Zhou, Yan wrote:
> The problem is that we have no way to enforce STARTTLS on 110, user can
> connect to DoveCot on port 110, sending user credential without STARTTLS
> (thus insecure). 
default_plaintext_auth = yes

It's the default.