Webmail
Author: Andrew Keating <[email protected]>
April 8, 2011

This application implements a simple HTTP server and SMTP client to enable 
sending email through a web interface. It is only intended for use on a LAN, as 
SMTP authentication is not supported.

To compile, execute ./compile.sh. Start the web server by executing ./run.sh. 
Java version >= 5 is required.

Usage notes:

After executing the application, http://localhost:8080 will present the user 
with a web form. Complete the form fields and press 'Submit' to attempt to send 
an email. If a value is entered in the 'Delay' field, the email will be sent 
after the input delay in seconds.

If an SMTP server is entered in the web form, the SMTP client attempts to 
connect to it on port 25. If no server is entered, a DNS MX lookup is performed 
on the domain of the recipient's email address and the result of the lookup (if 
any) is used as the SMTP server. Upon connecting, the SMTP client checks for a 
220 Service Ready code from the server, indicating a successful connection.

The status of all emails is stored by the application. When a delayed email is 
sent, it is initially considered to be “Pending,” and once the email has been 
sent, its status either changes to “Success” or an error message. When a user 
sends a delayed email, he/she is automatically forwarded to a dynamically-
generated status page, which displays the status of each email in a table. When 
a delayed email is sent, the application informs the sender via email. While 
not the epitome of user experience design, these were strict requirements of 
the university assignment.

Technical details:

The web server opens a TCP socket on Port 8080 and listens for HTTP requests. 
Incoming HTTP requests are validated, and a 400 Bad Request is returned if the 
HTTP is malformed.

In order to support international characters, the SMTP client implements the 
MIME quoted-printable encoding as described in RFC2045 [1]. Email lines are 
limited at 76 characters, and non-ASCII characters are encoded as an equals 
sign followed by the character's hexadecimal representation. Email subjects are 
encoded in an RFC2047-compliant format [2]. Conforming to RFC2821 [3], the SMTP 
client sends HELO, MAIL FROM, RCPT TO messages to the SMTP server and checks to 
ensure that 250 OK was received as a reply for each message. It then sends a 
DATA message and ensures that a 354 response code is received from the SMTP 
server. The SMTP client sends the email headers (to, from, subject and date), 
as well as MIME headers (MIME-Version, Content-Type, Content-Transfer-Encoding),
then completes the message by sending a blank line and a single period. If a 
250 OK is received in response, the SMTP client finally sends a QUIT message 
and disconnects from the SMTP server.

In SMTP, a line containing a period signals the end of a message's body. If a 
user sends an email containing a single period prior to the end of the email, 
truncation results. To avoid this, single periods in message bodies are 
replaced with double periods, a technique known as "dot stuffing."

[1] RFC2045 Multipurpose Internet Mail Extensions (MIME) Part One: Format of 
Internet Message Bodies - https://www.ietf.org/rfc/rfc2045.txt
[2] RFC2047 MIME (Multipurpose Internet Mail Extensions) Part Three: Message 
Header Extensions for Non-ASCII Text - https://www.ietf.org/rfc/rfc2047.txt
[3] RFC2821 Simple Mail Transfer Protocol - https://www.ietf.org/rfc/rfc2821.txt