O’Reilly news

"qmail": How To Say No to Monolithic MTAs

April 21, 2004

Sebastopol, CA--qmail has quietly become one of the most widely used applications on the Internet today. It's powerful enough to handle mail for systems with millions of users--like Yahoo! Mail and Hotmail--while remaining compact and manageable enough for the smallest Unix- and Linux-based PC systems. Its component design makes qmail easy to extend and customize while keeping its key functions secure. No wonder adoption of qmail continues at a rapid pace.

The downside? Apparently none. Except that qmail's unique design can be disorienting to those familiar with other popular MTAs (Mail Transfer Agents). Those coming from sendmail, for instance, might have trouble recasting their problems and solutions in qmail terms. qmail (O'Reilly, US $34.95), by John R. Levine, first helps readers establish a "qmail frame of mind," then explores the installation, configuration, administration, and extension of this powerful MTA. Whether they're performing an installation from scratch or managing mailing lists with thousands of users, qmail provides detailed information about how to make qmail do precisely what is needed.

"People who are familiar with other mail transfer agents, notably sendmail, rarely receive satisfactory results from qmail," notes Levine. "qmail was designed and written in a very different way from most other mail programs, so approaches used to solve problems with other programs don't work with qmail and vice versa." Levine explains that earlier MTAs were written as large, monolithic programs. sendmail, for example, is one large, executable program that listens for incoming SMTP connections, accepts local deliveries, interprets .forward files, retries mail for which earlier delivery attempts failed, and performs approximately fifty other functions. qmail, on the other hand, is made up of about ten small programs working together. According to Levine, it's a design approach that offers many advantages.

In qmail, Levine introduces the qmail essentials--how qmail works, where to find it, and how to get it running--then concentrates on explaining common tasks like moving a sendmail setup to qmail, or setting up a "POP toaster," a system that provides mail service to a large number of users on other computers sending and retrieving mail remotely. The book also fills crucial gaps in existing documentation, detailing exactly what the core qmail software does.

Topics covered include:

  • Installation and configuration, including patching qmail
  • Moving from sendmail to qmail
  • Handling locally and remotely originated messages
  • Managing virtual domains
  • Logging qmail activity
  • Tuning qmail performance
  • Running multiple copies of qmail on the same computer
  • Mailing list setup and management
  • Integrating the qmail MTA with POP and IMAP delivery
  • Filtering out spam and viruses
  • If you need to manage mailing lists, large volumes of mail, or simply find sendmail and other MTAs too complicated, qmail may be exactly what's called for. qmail provides the guidance qmail users need to build an email infrastructure that performs well, makes sense, and is easy to maintain.

    Additional Resources:

    John R. Levine
    ISBN 1-56592-528-5, 234 pages, $34.95 US, $50.95 CA
    1-800-998-9938; 1-707-827-7000

    About O’Reilly

    O’Reilly Media spreads the knowledge of innovators through its books, online services, magazines, and conferences. Since 1978, O’Reilly Media has been a chronicler and catalyst of cutting-edge development, homing in on the technology trends that really matter and spurring their adoption by amplifying “faint signals” from the alpha geeks who are creating the future. An active participant in the technology community, the company has a long history of advocacy, meme-making, and evangelism.

    Email a link to this press release