Back in the good ol’ days of POP3 it was really easy to test a mail server manually you just simply telnet to port 110 issue some 3 command and done! Now that all ISPs support IMAP things are a little more complicated. Here’s my little guide to manually testing POP3, IMAP and SMTP

Testing POP3

POP3 testing is really really simple, here’s an example (The command I entered are in bold):

[adam@desktop ~]$ telnet zippy.deaconsworld.org.uk 110
Trying 10.0.0.1...
Connected to zippy.deaconsworld.org.uk.
Escape character is '^]'.
+OK Dovecot ready.
user <username>
+OK
pass <password>
+OK Logged in.
list
+OK 185 messages:
1 34718
<snip>
185 20419
.
top 1 0
+OK
Return-path: <someone@example.com>
Envelope-to: <someonelse@example.com>
Delivery-date: Mon, 20 Oct 2008 15:02:43 +0100
Received: from outbound.mse17.exchange.ms ([64.71.238.253])
    by zippy.deaconsworld.org.uk with esmtps (TLSv1:RC4-MD5:128)
    (Exim 4.69)
    (envelope-from <someone@example.com>;)
    id 1KrvLE-0001Fq-PT
    for <someonelse@example.com>; Mon, 20 Oct 2008 15:02:43 +0100
<snip>
.
quit
+OK Logging out.
Connection closed by foreign host.
Here’s a list of some useful commands and their explanations:

  • user [username] - Sends the username for the connection
  • pass [password] – Sends the password for the connection
  • list – Displays a list of email ID and their sizes.
  • top [id] [length] – Gets the “top” of an e-mail. The ID is from the list command (the first e-mail is always 1). top always gets the headers and then [length] lines e.g. top 1 0 will get just the headers of the first e-mail or top 2 10 will get the headers and the first 10 lines of e-mail 2.
  • retr [id] – Gets the whole of e-mail.
  • dele [id] – Deletes an e-mail
  • quit – closes the connection

Testing IMAP

IMAP is a little more complicated because of folders and because it’s asynchronous. After telnetting to port 143, here’s an example:

[adam@desktop ~]$ telnet zippy.deaconsworld.org.uk 143
Trying 10.0.0.1...
Connected to zippy.deaconsworld.org.uk.
Escape character is '^]'.
* OK Dovecot ready.
1 login <username> <password>
1 OK Logged in.
2 select "INBOX"
* FLAGS (\Answered \Flagged \Deleted \Seen \Draft unknown-1 unknown-0 Junk receipt-handled NonJunk $MDNSent)
* OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft unknown-1 unknown-0 Junk receipt-handled NonJunk $MDNSent \*)] Flags permitted.
* 185 EXISTS
* 0 RECENT
* OK [UNSEEN 183] First unseen.
* OK [UIDVALIDITY 1220688986] UIDs valid
* OK [UIDNEXT 3859] Predicted next UID
2 OK [READ-WRITE] Select completed.
3 FETCH * ALL
* 185 FETCH (FLAGS () INTERNALDATE "07-Nov-2008 09:51:29 +0000"...
3 OK Fetch completed.
4 logout
* BYE Logging out
4 OK Logout completed.
Connection closed by foreign host.
Here you’ll notice the numbers at the start of each line. This technically should be a unique string for each command, the server will reply with the same number. In reality, you can use the same number for each line. As before here’s a list of useful commands you might need:

  • LOGIN “[username]” “[password]“ – sends the username/password
  • SELECT “[folder]“ – Selects the folder to use. I always use INBOX as this should always exist
  • FETCH * ALL – Gets all the heads for the first message
  • LOGOUT – Closes the connection

Testing SMTP

Just for completness here’s a test for SMTP. After telnetting to port 25, try the following:

[adam@desktop ~]$ telnet zippy.deaconsworld.org.uk 25
Trying 10.0.0.1...
Connected to zippy.deaconsworld.org.uk.
Escape character is '^]'.
220 zippy.deaconsworld.org.uk ESMTP Exim 4.69 Fri, 07 Nov 2008 11:18:45 +0000
ehlo adam
250-zippy.deaconsworld.org.uk Hello adam [10.0.0.28]
250-SIZE 52428800
250-PIPELINING
250-AUTH LOGIN
250-STARTTLS
250 HELP
mail from: adam@deaconsworld.org.uk
250 OK
rcpt to: adam@deaconsworld.org.uk
250 Accepted
data
354 Enter message, ending with "." on a line by itself
Subject: test

test
.
250 OK id=1KyPMm-00078C-9u
quit
221 zippy.deaconsworld.org.uk closing connection
Connection closed by foreign host.
The above should send a test message, however it’s not exactly RFC2822 complient so don’t be surprised if spam filters drop it.