imap server fetch not working properly - email

Question

I'm currently working on my own IMAP server.
When i get a FETCH request for 3 mails and i send a response with 3 mails, the client does not seem to recognise my response. (my client reports that there is no mail)
This is the request and response (C is client, S is server):
C: 405 UID FETCH 4,3,1 (INTERNALDATE RFC822.SIZE FLAGS BODY.PEEK[HEADER.FIELDS (subject from date content-type to cc message-id references importance reply-to)])
S: * 3 FETCH (UID 4 RFC822.SIZE 332 INTERNALDATE "<date>" FLAGS (\Recent) BODY[HEADER.FIELDS (SUBJECT FROM DATE CONTENT-TYPE TO CC MESSAGE-ID REFERENCES IMPORTANCE REPLY-TO)] {317}
Subject: <subject>
From: <email>
Date: <date>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
To: <email>
CC: <email>
Message-ID: <messid>
Reply-To: <email>
)
S: * 2 FETCH (UID 3 RFC822.SIZE 731 INTERNALDATE "<date>" FLAGS (\Recent) BODY[HEADER.FIELDS (SUBJECT FROM DATE CONTENT-TYPE TO CC MESSAGE-ID REFERENCES IMPORTANCE REPLY-TO)] {231}
Subject: <subject>
From: <email>
Date: <date>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Message-ID: <messid>
Reply-To: <email>
)
S: * 1 FETCH (UID 1 RFC822.SIZE 400 INTERNALDATE "<date>" FLAGS (\Answered \Recent) BODY[HEADER.FIELDS (SUBJECT FROM DATE CONTENT-TYPE TO CC MESSAGE-ID REFERENCES IMPORTANCE REPLY-TO)] {252}
Subject: <subject>
From: <email>
Date: <date>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
To: <email>
Message-ID: <messid>
Reply-To: <email>
)
S: 405 OK UID FETCH completed
where (subject) is the actual subject, (email) are valid emailadresses, (date) is the date and (messid) is a unique message-id.
Does somebody see what i am doing wrong here. maybe i am sending the wrong response, or am i doing something else wrong?
can someone help me with this?
so far, anything else (login, list, search) works fine. if it is needed, i could send those requests/responses as well
thanx i advance.