Testing Mail Services

SMTP

Connect to the server you wish to test:

$> telnet mailserver.example.com smtp

The server should reply with:

Trying mailserver.example.com...
Connected to mailserver.example.com.
Escape character is '^]'.
220 mailtest ESMTP Postfix (Debian/GNU)

Great! Postfix is listening and wants us to speak SMTP. First we need to be friendly:

ehlo example.com

Postfix appreciates our friendliness and tells us which features are available:

250-my-new-mailserver
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN

Hey, Postfix, we have a mail from steve@example.com:

mail from:<matt@example.com>

Looks like Postfix is happy with that because return codes that start with a '2' are good news:

250 2.1.0 Ok

Tell Postfix who the recipient of the mail is:

rcpt to:<clark@example.com>

Postfix accepts that:

250 2.1.5 Ok

Then we are ready to send the actual mail:

data

Postfix agrees and tells us we can send the actual mail now and end our input with a dot on an empty line:

354 End data with <CR><LF>.<CR><LF>

Okay, now type up an e-mail:

Hi Matt,

Just wanted to drop you a note.
.

Postfix tells us it has received the mail and queued under a queue ID:

250 2.0.0 Ok: queued as A9D64379C4

Thanks, Postfix, we are done:

quit

POP

Let us try to create a POP3 connection and retrieve Matt's email:

$> telnet localhost pop3

The server replies:

Trying mailserver.example.com...
Connected to mailserver.example.com.
Escape character is '^]'.
+OK Dovecot ready.

Login as Matt:

user matt@example.com

The server should accept that:

+OK

Send the password:

pass summersun

The server should recognize the correct password:

+OK Logged in.

Get a list of John's emails:

list

Dovecot will tell you that one email is in the mailbox:

+OK 1 messages:
1 474
.

Fetch that email number 1:

retr 1

Dovecot sends you the email:

+OK 474 octets
Return-Path: <clark@example.com>
X-Original-To: matt@example.com
Delivered-To: matt@example.com
Received: from example.com (localhost [127.0.0.1])
    by ... (Postfix) with ESMTP id 692DF379C7
    for <matt@example.com>; Fri, 18 May 2007 22:59:31 +0200 (CEST)
Message-Id: <...>
Date: Fri, 18 May 2007 22:59:31 +0200 (CEST)
From: clark@example.com
To: undisclosed-recipients:;

Hi Matt,

Just wanted to drop you a note.
.

Close the connection to the POP3 server:

quit

The server will disconnect you:

+OK Logging out.
Connection closed by foreign host.

IMAP

$> telnet mailserver.example.com 143

You should get a connection:

Trying mailserver.example.com...
Connected to mailserver.example.com.
Escape character is '^]'.
* OK Dovecot ready.

IMAP commands always start with a number and reply to that command with the same number. So the following commands must be entered with the number at the beginning of each line.

Login with username and password:

1 login matt@example.com summersun

Dovecot logs you in:

1 OK Logged in.

Ask Dovecot for a list of John's mail folders:

2 list "" "*"

Here comes the list:

* LIST (\HasNoChildren) "." "INBOX"
2 OK List completed.

Select your inbox:

3 select "INBOX"

Dovecot gives you all kinds of information about that folder:

* FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
* OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft \*)] Flags permitted.
* 1 EXISTS
* 0 RECENT
* OK [UIDVALIDITY 1180039205] UIDs valid
* OK [UIDNEXT 3] Predicted next UID
3 OK [READ-WRITE] Select completed.

You see that one email exists. Fetch it:

4 fetch 1 all

IMAP will just give you basic information on the email:

* 1 FETCH (FLAGS (\Seen) INTERNALDATE .........
4 OK Fetch completed.

To read the actual mail body you need to fetch it exlicitly:

5 fetch 1 body[]

Here it comes:

* 1 FETCH (BODY[] {474}
Return-Path: <clark@example.com>
X-Original-To: matt@example.com
Delivered-To: matt@example.com
Received: from example.com (localhost [127.0.0.1])
        by ... (Postfix) with ESMTP id 692DF379C7
        for <matt@example.com>; Fri, 18 May 2007 22:59:31 +0200 (CEST)
Message-Id: <...>
Date: Fri, 18 May 2007 22:59:31 +0200 (CEST)
From: clark@example.com
To: undisclosed-recipients:;

Hi Matt,

Just wanted to drop you a note.
)
5 OK Fetch completed.

Disconnect from the server:

6 logout

Dovecot logs you out:

* BYE Logging out
6 OK Logout completed.
Connection closed by foreign host.