I'm having a problem connecting to an IceWarp Server using IMAP.

Question

I’m getting the following exception when trying to connect using the IMAP Mailbox Browser sample app on one of my customer’s machines:

Rebex.Net.TlsException: Fatal error 'HandshakeFailure' has been reported by the remote connection end.--> Rebex.net.TlsException:
...

This is with the port set to 993, implicit TLS/SSL, and I'm allowing SSL 3.0 protocol and all ciphers.

On the same machine, I can connect with Outlook 2010 using these settings:
Incoming Server (IMAP): 993
Use the following type of encrypted connection: SSL

I've tried other combinations of settings in the IMAP Mailbox Browser, and they either timeout, or they get the error:

Server reported error:
AUTHENTICATE Unknown user or incorrect password (NO).

What needs to be done to connect to this IMAP server?

Comments

See my answer below. It looks like emails that we sent to you from our support@rebex.net email account nor from our alternative gmail address got lost somehow. Please check your email client settings and also possibly spam folders to make sure that you will be receiving emails from us.

Answer 1

Have you tried connecting using TLS 1.0, 1.1 or 1.2? SSL 3.0 is an unsecure legacy protocol that should no longer be used (see http://disablessl3.com/ for more information).

It looks like we have forgot to update the ImapBrowser sample to reflect this (and TLS 1.1 and 1.2 are missing in the Settings dialog), but you can easily try the more recent protocols by modifying the following line in Worker.vb file and recompiling:

_imap.Settings.SslAllowedVersions = CType(_config.GetValue("protocol", GetType(TlsVersion)), TlsVersion)

Try changing this to:

_imap.Settings.SslAllowedVersions = TlsVersion.TLS10 Or TlsVersion.TLS11 Or TlsVersion.TLS12

Please let us know whether you are able to connect with the ImapBrowser sample after enabling all TLS 1.0, TLS 1.1 and TLS 1.2 versions.