How to connect IMAP using AUTHENTICATE PLAIN correctly?

I'm using OpenSSL to connect to mail server.

POP3 works fine but I have problems with IMAP. Based on CAPABILITY command server supports PLAIN, NTLM and GSS-API authentication methods.

I want to use PLAIN because it's easier than others. I have read it's needed to use <NUL> for it.

I have run the next variations, but no success:

? login user pass
? login <nul>user<nul>pass
? <nul>login <nul>user<nul>pass

What am I doing wrong?

Solution

? login mymailbox@box.zone mypassword\r\n

often servers don't require " @box.zone " part, you can just type login