IMAP works but IMAP TLS doesn't under PHP (Horde IMP)
 

I've been trying to get Secure IMAP working under Horde Webmail without any luck.

I currently have IMAP authentication (without encryption) working using the below without a problem, it is just when I try to use IMAP TLS, it doesn't authenticate correctly (i don't know how to check any more than that.. i don't have physical access to the [NT] mail server :o).

My 'architecture' is as follows:
A Linux box runs as the webserver (Apache 2.0.40-21.5) with the webmail client (Horde IMP 3.2 under PHP 4.2.2-17.2) on an internal network (network 1). The box then establishes a connection to an external static ip [via a linux router] to a port [specified above 40000] on that linux router (network 2), which in turn, masquerades the [tcp/udp] connection to an internal mail server (running MS Exchange 5.5.2653.13 under NT).
Just to note: It is not possible to create a secure tunnel between the 2 networks :o :(

Webserver
|
| (network 1)
Router
|
---------
INTERNET
---------
|
Router
| (network 2)
|
Mail Server

I'm using IPCHAINS (1.3.10-10) on the second router and ipmasqadm (0.4.2-4) to masquerade connections from the network1 to the internal exchange mail server on network 2.
I'm using a port [above 40000] for masquerading because we already have a TLS server accessable on port 993 to the outside on the second router.

I'm gussing, ... that possible causes as to why IMAP TLS doesn't work could be:....
- IMAP TLS negotiations can 'only' occur on port 993?
- Horde IMP WebMail doesn't support IMP TLS to an exchange server?
- IMAP TLS uses both UDP and TCP for transport?
... too many others

Any Horde IMP server configuration examples out there using IMAP TLS/SSL for an exchange server?
Any examples from anyone with an external webserver to internal mail server?
Any masquerading thoughts on using IMAP TLS?

It's a mess I know :( Sorry
(I've got so many other important things on my mind atm !:'( )