Test your IMAP server with Telnet

     Internet Message Access Protocol version 4 (IMAP 4 ) is an email retrieval protocol which is a lot more robust than the Post Office Protocol version 3 ( POP3).   It provides features like name spaces,folders,sub folders,flags etc.. A discussion of all the features is beyond the scope of this article.  Here we will see how we can test the basic functionalities of an IMAP server using telnet.

     First, establish a connection to the IMAP server using telnet on port 143.

safeer@penguinpower:~$ telnet imap.safeer.in 143
Trying 10.25.0.3...
Connected to imap.safeer.in
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THREAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION] Courier-IMAP ready. Copyright 1998-2011 Double Precision, Inc.  See COPYING for distribution information.

     The last line of the output is a greeting from the IMAP server.  Further conversation with the IMAP server will be a series of requests and responses.   Requests are also known as commands and should begin with an arbitrary tag (an alpha numeric string ) followed by a command and its optional arguments, all separated by spaces.  The response, if positive will be the request tag name followed by OK and further by a server message.  This is for a single line response.  If the response is multi line, all except the last line with begin with a "*" and the last line will be request tag followed by OK and then server message.  A negative response will begin with request tag followed by a "NO" and a server message.

     To test the IMAP server at a minimum we should login,select INBOX, retrieve a message and logout.  Let us start by providing a tag followed by the command "login" followed by the IMAP username and password, all separated by spaces.

A01 LOGIN safeer fake_Password
A01 OK LOGIN Ok.

     With IMAP, you can have multiple mailboxes.  "INBOX" is the default and only one mailbox if you have not configured additional mailboxes.  Let us see the mailboxes and its sub folders using list command.  It takes two arguments, first being the folder to list and the second being a search parameter.  Since we are looking for mail boxes, we should be searching the root of the IMAP indicated by a blank "".  The search parameter is a wildcard ( "*" ) here since we want to see all folders under the root.

A02 list "" "*"
* LIST (\Marked \HasNoChildren) "." "INBOX"
1 OK LIST completed

     This is a multi line response from the server and it says there is only one mailbox "INBOX" with no sub folders.  Now let us see the  status of the "INBOX" and find out the number of messages in it.

A03 STATUS INBOX messages
* STATUS "INBOX" (MESSAGES 1)
A03 OK STATUS Completed.

     There is only one message in the INBOX. In order to view messages in the mailbox INBOX ( or any IMAP folder for that matter ) we should first select the folder.

A04 SELECT INBOX
* FLAGS (\Draft \Answered \Flagged \Deleted \Seen \Recent)
* OK [PERMANENTFLAGS (\* \Draft \Answered \Flagged \Deleted \Seen)] Limited
* 1 EXISTS
* 1 RECENT
* OK [UIDVALIDITY 1358664910] Ok
* OK [MYRIGHTS "acdilrsw"] ACL
A04 OK [READ-WRITE] Ok

     In the response, 1 EXISTS means there is only one message in INBOX and 1 RECENT means that 1 message is unread.  We can list/read the emails by using the fetch command.    Let us read the message ( since there is only one message in the INBOX, the id of the message will be 1 and that is passed as an argument to fetch command).  Let us first view the email headers.

A05 FETCH 1 body[header]
* 1 FETCH (BODY[HEADER] {501}
Return-Path: <info@safeer.in>
X-Original-To: safeer@safeer.in
Delivered-To: safeer@smtp.safeer.in
Received: from penguinpower (penguinpower [128.1.0.5])
    by smtp.safeer.in (Postfix) with ESMTP id AD10226089C
    for <safeer@safeer.in>; Thu, 10 Feb 2011 00:42:29 +0530 (IST)
Subject: POP3 Check
Message-Id: <20110210191235.AD10226089C@smtp.safeer.in>
Date: Thu, 10 Feb 2011 00:42:29 +0530 (IST)
From: info@safeer.in

)
* 1 FETCH (FLAGS (\Seen \Recent))
A05 OK FETCH completed.

     You can see the message headers.  Now let us read the message text.

A06 FETCH 1 body[text]
* 1 FETCH (BODY[TEXT] {14}
Testing POP3
)
A06 OK FETCH completed.

     We are done retrieving the message.  Note that fetch command can operate on a single message id or a range or ids in the format START:END.

    Now logout of the session:

A07  LOGOUT
* BYE Courier-IMAP server shutting down
A07 OK LOGOUT completed
Connection closed by foreign host.

    To know more about IMAP checkout the IMAP RFC at ITEF