Error 535 Authentication failed when using AuthPla (wodSmtpServer / wodPop3Server / wodImapServer)

Hi,

I am writing an email server by using C# at the moment but I am having a problem when I use Plain Authentication.

The email client that I am using can support LOGIN, NTLM, CRAM MD5, PLAIN and MSN authentications.

On my code, I have used:-

Smtp.Authentication = SmtpAuthentications.AuthPlain;

and there is a method called 'Smtp_Authenticate' that is used to valid the username and password and decide the action.

Once I am using PLAIN authentication from this email client, I will have an error 535 Authentication failed displayed on the client. When I set a break point within my code, my server will not process the 'Smtp_Authenticate' method at all. It stops at another method called 'Smtp_Command'.

If I use User.Transcript property within this 'Smtp_Command' method, I will get the followings:-

User 127.0.0.1 issued command EHLO ABC
250-ABC Hello ABC [127.0.0.1], nice to meet you
250-EXPN
250-HELP
250-AUTH PLAIN
250-PIPELINING
250 8BITMIME
AUTH PLAIN

Would you please tell me what is happening at there? and how to solve this?

Thanks,
Yan.