The following content was forwarded to me by Saurabh. Originally written by Shuvam, this article brings out the differences between Postmaster and Mtracks, and is really very informative. I thought that it would be a good idea to put this content here so that everyone benefits. 

1.  Postmaster handles only email, while Mtracks handles Web access too.
    This alone is the largest difference between the two, and this makes
    Mtracks much more well suited to small offices.

    Once this difference is highlighted, all the features from the
    "Mtracks Features Summary" white paper related to the Web access and
    proxy control can be explained to the client.

2.  Postmaster works (primarily) on Windows PCs, while Mtracks works on
    Linux. The added security, virus-resistance, stability, and
    reliability of Linux is an added benefit in the Mtracks solution.

3.  Postmaster usually works on Windows desktop OS, which are specially
    insecure and unstable. It is also possible to make Postmaster work
    on Windows server class OS, e.g. Win2K3, but then the licence fees
    of Win2K3 becomes quite high. Mtracks on the other hand works on
    Linux, which is a server-class OS to begin with, and has no separate
    licence fees for Linux.

4.  Postmaster does not have a browser-based administration interface;
    all administration typically has to be done sitting at the console
    of the computer which is running the Postmaster software. This is
    not necessary with Mtracks; you can manage it sitting anywhere.

5.  Postmaster fetches emails only through POP3 accounts which are set up
    on some ISP's server. If your office has a permanent IP address and
    leased Internet link, in theory it can receive direct incoming
    emails from the Net, but Postmaster cannot handle this. You are
    forced to receive mails via a POP3 account somewhere on some other
    server totally unnecessarily. Mtracks can fetch messages from POP3
    accounts as well as receive direct email.

6.  Mtracks gives the customer the option of receiving compressed UUCP
    email. UUCP over TCP allows incoming email to come in via Starcom's
    MX servers, without the customer needing a POP3 account anywhere or
    a permanent IP address. UUCP is much more reliable than POP3 mail
    fetching, and large messages (greater than 20MB) can easily come in
    over UUCP even if the Internet link breaks in between. When fetching
    mails from a POP3 mailbox, if the connection breaks in the middle of
    a large email, the entire message has to be re-fetched, thus wasting
    time and money and blocking up the subsequent messages. With UUCP,
    the system restarts the download at the point where the connection
    broke.

7.  Mtracks keeps all metadata in a relational database. This allows
    future integration of this data with ERP systems, billing systems,
    etc. One of our clients is building a large set of business
    applications including financial accounting systems, for internal
    use. They want to use the Mtracks database for user authentication
    and password validation for all these applications, so that a sort
    of single-signon and a unified user database is possible.

8.  Mtracks provides IMAP4 support, which Postmaster does not. IMAP4
    allows all users to keep their mail folders, including old mails, on
    the server. This means that valuable mails don't get lost when a
    desktop's hard disk crashes. It also means that a user can move from
    one desktop to another and still access all his mails, because they
    reside on the server.

9.  The Webmail feature on the Postmaster system is of very little use.
    It can only show you the new messages in the Inbox, but can't let
    you access the old messages which are there in the rest of the mail
    folders, because Postmaster does not store old messages and user
    folders on the server. All these folders are forcibly kept on the
    desktop computer's hard drive. With Mtracks, you get IMAP4, where
    you can store mail folders on the server, and all these mails can be
    later viewed, forwarded, or replied to using Webmail.

10. Mtracks provides a LDAP-based address book for users. This address
    book can also contain external email addresses for outside parties,
    thus allowing a common enterprise-wide address book. Postmaster does
    not provide an address book at all.

11. Mtracks provides you a vacation facility, wherein a user can set up
    an automatic response to all his incoming messages when he is away
    from office (typically on vacation, hence the name of the facility).
    Postmaster has no such feature.

12. Mtracks has a reminder feature, which Postmaster does not have. We
    have usually found that reminders are a very powerful feature which
    users become totally dependent on, once they begin using it.

13. Password change reminder and expiry: Mtracks sends a reminder to
    users who have not changed their passwords for a long time. The gap
    duration after which these reminders are sent can be set by the
    system administrator. If the user does not change his password after
    repeated reminders, his account can be blocked automatically by
    Mtracks. This is an important security feature. Postmaster does not
    have any of these features.

14. An Mtracks server can act as a file and print server, where the
    userID and password which is used for email can be used for
    accessing a user's files too.
15. Mtracks supports auto-collection of email addresses, a feature which
    is not provided by Postmaster.

16. Mtracks provides an anti-virus scanner as part of the package, while
    this is a separately priced option with Postmaster.

17. Mtracks servers can be set up to work in redundant pairs. In this
    situation, one server will be active (or primary) and the other
    will be in backup mode. The backup server will periodically pull out
    all data from the primary server and make a mirror copy. This works
    automatically. If the primary server fails, the backup server can be
    made primary in about three to five minutes, and email services can
    continue. Postmaster has no such feature.

18. Starcom provides the services of incoming mail reception through its
    MX servers, and outgoing mail transfer through its outgoing SMTP
    servers. These services have various advantages like bandwidth
    conservation, and can address many situation which would be
    problematic with more conventional solutions like Postmaster.

In summary, Postmaster appears to be a sort of toy application, not
really designed for large enterprise use. An organisation which becomes
a mature user of email will typically begin to demand greater features,
greater control, and greater integration than what Postmaster provides.
Mtracks is a better answer.