Canot open connection to IMAP with TLS encryption



11 years ago
10 years ago


(Reporter: Yves Goergen, Unassigned)


Windows XP

Firefox Tracking Flags

(Not tracked)


(Whiteboard: closeme 2008-08-28)


(1 attachment)



11 years ago
User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv: Gecko/20070914 Firefox/
Build Identifier: 

I have set up 3 IMAP accounts on the same server. All of them are configured to use TLS encryption. I can connect to the first one, when trying to connect to the others, Thunderbird says it canont connect. Since copying the tex doesn't work, I have attached the error message. Bt it's totally useless anyway.

It all works fine when I disable TLS but I really don't want to to this!

On another computer on this net, it works fine. Also, the error message says, there are probably too many connections, but it's not true. I have set the limit on the server to 50 or so.

Reproducible: Always

Steps to Reproduce:

Comment 1

11 years ago
Created attachment 282271 [details]
Error message screenshot

Comment 2

11 years ago
More information:

After starting Thunderbird on the problematic computer, I can connect to exactly one IMAP account. Every further attempt with another account fails.

When I close Thunderbird on another computer on the same local network, thus closing 3 IMAP TLS connections to the same server, I can connect to a second account on the problematic computer. A third connection attempt, however, still fails.

A check with Sysinternals' TcpView showed that Thunderbird indeed opens a connection to the remote host but immediately closes it again as the error message shows up.

Also, I'm currently investigating on the server side, but I can't find that configuration option anymore where I remember to have set a connection limit long ago. It's a Courier-IMAP server running on Debian Linux. I can vaguely remember that there has been a war between the Thunderbird and Courier-IMAP teams blaming each other for their incompetence or something. But however, I'd still like to see a solution to this problem until I am finished with my own e-mail client.

Debugging the IMAP session on the network layer doesn't seem possible because of the TLS encryption, so I can't tell what the client and server are actually talking.


10 years ago
Version: unspecified → 2.0
Thunderbird has IMAP logging.  There's a web page somewhere that tells how
to turn it on.  Sorry, I don't have the URL handy.  It works both with 
and without SSL (since it's on the plaintext side of the channel). 
Need to try it next.  If THAT shows evidence that the problem is SSL/TLS
handshake failure, then the next step is to use the ssltap program to 
capture the handshake details.  

Also, please add a comment with all information about the exact product,
version, etc of the server in question.  There are some servers that are 
known to do TLS improperly, and to do SSL 3.0 in the presence of a TLS 
compatible client hello improperly.
The page with info on enabling logging is here:
Babelfish's translation of that German error text into English:

Could not connect to your IMAP server. They possibly exceeded the maximum 
number from connections to this server. If this is the case, use the dialogue 
for extended IMAP server attitudes, in order to reduce the number of upright 
received connections.


Comment 6

10 years ago
Yves, need your log per comment 4

Comment 7

10 years ago
Reporter hasn't been back in nearly a year to help with providing a log, so I'm proposing we resolve the bug as incomplete if we don't hear back in the next couple of weeks.
Whiteboard: closeme 2008-08-28
RESO INCO per lack of response to the last question. If you feel this change was made in error, please respond to this bug with your reasons why.
Last Resolved: 10 years ago
Resolution: --- → INCOMPLETE
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