Thunderbird cannot connect through proxy

[Guest]

At work I have to access the Internet through a proxy. With Firefox this works fine, but with Thunderbird I cannot connect to my personal IMAP server.
A telnet session (using putty) to my server works without any problem. Thunderbird, however, keeps reporting that it "Failed to connect to server xxx".
I hope someone can help me solve this problem.

[Guest]

Doens't anybody have at least an idea?

[rsx11m]

If your proxy server provides it, you could try a SOCKS proxy that allows you to connect to your remote mailbox. The Thunderbird settings for the SOCKS server are in the Tools->Options->Advanced->Network->Connection dialog, just underneath the HTTP proxy settings. Below an older post, but a similar problem, and it explains in more detail how it works - http://forums.mozillazine.org/viewtopic ... 24#1259898

If a direct access with IMAP/SMTP through SOCKS is not possible, but your provider has some webmail option (and there is a TB extension for it), you could try this as workaround instead over your HTTP proxy. In either way, you should consult with the administrator of your private network what the best way is to connect to your personal mail box, since he or she may have to configure and authorize this for you.

[Guest]

If your proxy server provides it, you could try a SOCKS proxy that allows you to connect to your remote mailbox. The Thunderbird settings for the SOCKS server are in the Tools->Options->Advanced->Network->Connection dialog, just underneath the HTTP proxy settings. Below an older post, but a similar problem, and it explains in more detail how it works - http://forums.mozillazine.org/viewtopic ... 24#1259898

If a direct access with IMAP/SMTP through SOCKS is not possible, but your provider has some webmail option (and there is a TB extension for it), you could try this as workaround instead over your HTTP proxy. In either way, you should consult with the administrator of your private network what the best way is to connect to your personal mail box, since he or she may have to configure and authorize this for you.

I'll try that. Still, I don't understand why I can use telnet to contact my IMAP server while Thunderbird cannot.

[rsx11m]

When you telnet to your IMAP server, are you using the correct port? (143/tcp for unencrypted and 993/tcp for encrypted transmissions) If you can connect directly from your machine to the server on the correct port, you wouldn't need any proxy inbetween. In this case, the firewall would simply be forwarding your IMAP and SMTP requests from the internal to the external network (e.g., using NAT).

[Guest]

Yes, I'm using telnet on 143 and I've set the proxy settings in PuTTy.

[rsx11m]

Ah, ok! Are you using an HTTP proxy to connect to your IMAP server? As far as I can tell, this can't work, since the HTTP proxy can only "talk" the HTTP protocol. Meaning, you get a connection established to your IMAP server, but provide it with HTTP requests which that server (correctly) refuses. I'm not aware of any way to tunnel the IMAP protocol over HTTP, other than using a webmail extension as suggested for a workaround in my initial response.

Also, be aware that port-143 IMAP (and port-25 SMTP for that matter) will transfer your user name and password in clear text, making eavesdropping easy. Thus, always use SSL or TLS encryption whenever your server provides it.

[Guest]

HTTP proxy can pass-through almost any protocol using the CONNECT method. The proxy simply tunnels the data to the server as-is without any modification. IMAP and SMTP can be connected over an HTTP proxy with no problem.

[Guest]

The reason is probably because you have no DNS configuration that can resolve domains in the world outside your local network.

Try to resolve some publicly known domains (for example, google.com or yahoo.com) using `nslookup` command line. If you cannot get the IP - the DNS is not configured properly.

[Daifne]

Er, Guest, did you happen to notice how old this topic is? I doubt that anyone is watching this after two years. Locking.