Mail: Linux + Postfix + Dovecot + SASLAuthd

Question

Our corporate Fedora 10 (Linux) server is set up running Postfix and Dovecot, with SASLAuthd authentication and a self-signed certificate. There is only IMAPS service, no POP3 or IMAP.
Typically, a client (i.e. Thunderbird, Outlook, etc.) will be set up like so:
Email Address: [email protected]
User Name: user1
Server: incoming.example.com
IMAPS Port: 993
Using SSL: YES
We have a new high-level (VP) employee with a 3G iPhone. No matter what we try, we cannot get his iPhone to successfully connect to the IMAPS service. We're not concerned with the outgoing mail, as he normally uses AT&T's cwmx.com for that.
The error we receive on the iPhone is:
Could not collect mail: Cannot connect to server incoming.example.com
The error we receive in our /var/log/maillog is:
dovecot: imap-login: Disconnected (no auth attempts): rip=32.173.26.227, lip=MAI.LSE.RVE.RIP, TLS
What do I need to do to the iPhone to get it to send an auth request and collect his mail? He is adamant about using this device for mail.
Thank you in advance.
James

Answer 1

I could accept the possibility of a certificate problem if there had been any issues with the certificate at any point prior to this, but this has been an active server running this setup for over 4 years, and the only user to ever have a problem connecting is our single iPhone user.
To update, I have modified the accepted authentication mechanisms to include these:
Digest-MD5
Cram-MD5
Plaintext (the original)
Changing the settings on the iPhone to what it calls "HTTP MD5 Digest" or MD5 Challenge-Response" produces the same result, highlighted here:
(no auth attempts)
This seems to indicate, at least from the server's perspective and coming as I do from a non-Mac position, that the iPhone did not even try any authentication mechanism. At least that is what it usually means. I have extended logging enabled while we troubleshoot this, but I am getting nothing but that one error.
If I may be so foolish as to offer an analogy, it's kind of like this:
A person approaches a house.
They knock on the door.
From inside, they hear, "Who is it?"
They say nothing.
Again, through the closed door they hear: "Who is it?"
They still say nothing.
Obviously the door never opens, and the person inside loses interest and stops asking who it is, due to the lack of response from the person outside.
So that's my analogy. I just want this iPhone to TRY to authenticate.