It looks like this server's implementation of CRAM-MD5 authentication is broken. Both Outlook and FoxMail try classic cleartext authentication instead and this works in Rebex POP3 as well. You just need to explicitly specify the authentication method in the
Login method call. In the Pop3Download sample's source code, find the following line:
client.Login(config.User, config.Password, Pop3Authentication.ClearText);
This should solve the issue. We will add a workaround for it to the next release. Thanks for reporting this!
Update: The workaround is available in Rebex Secure Mail 2012 R3. With this release, it's no longer necessary to explicitly specify