[RESOLVED] SMTP Conversation

[chris128]

Following on from this thread - http://www.vbforums.com/showthread.php?t=580359 (which follows on from another one..) I am trying to make my own SMTP server and am having a few problems.

I'm using the TcpClient and TcpListener classes to read/write to the network when a request comes in on port 25. All I'm trying to do at the moment is make it so that my server program can receive SMTP messages from other SMTP servers. I've tested in Telnet - if I connect to my own IP on port 25 and type EHLO, MAIL FROM, RCPT TO, DATA etc then all works as it should and the details I entered are logged by the program (it doesnt do anything about delivering these details/email yet).
So all looks good... but then when I try and just send an email to my domain from my work account I can see that a connection is made to my program and the string "EHLO workdomain.com " is received by my program - my program responds to the remote SMTP server with "250-mydomain.com Hello" and then a CrLF and then "250-OK". After that point however, my app does not receive anything further at all from the server at work. I'm guessing I am doing something wrong with the data I'm returning when it sends EHLO but can anyone point me in the correct direction?
I can post code if necessary but I dont know if that will help really

Thanks
Chris

EDIT: Ah, I've just found the cause of one problem... because I was using telnet to test with, it seems that I have made it work only with telnet... In telnet each time I type a key the data is passed to the server, however with a real SMTP server it just sends each entire command in one go. So after altering my server a little I can now get it to respond with the 250-OK which I thought it already was doing.. but it still doesnt work. The remote server just sends EHLO and then thats it nothing more

EDIT EDIT: Something interesting, at the moment I am ending all of my responses to the remote server with VbLf - if I change this to VbCrLf (which is what I believe it is meant to be according to the SMTP standard) then I get an infinite amount of empty strings sent to my program (or perhaps some other character that just shows as an empty string in intellisense when stepping through the code). Changing it back to just vbLf or ControlChars.Lf makes it go back to just sending EHLO and then nothing else..