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Delivering security and performance

In the area of Mail Transfer Agents (MTAs), most people would look at sendmail as the most popular solution in the open source/Linux arena. However, it's not the only solution. Although postfix is popular with a number of administrators (especially those with multiple domains and many users), qmail is the unknown underdog that the experts use.

John Levine, well-known book author and Internet guru, talks about his new book, qmail, which covers the entire gamut of qmail administration from installation to configuration and filtering.

LWM: Another title in the successful mail-management series. Can you tell me the main benefits of qmail over other MTAs such as sendmail?

John Levine: qmail's two strongest points are security and performance. qmail was designed and written by a computer security geek, and is small enough so that if you want, you can read all the source. There's never been a security bug in qmail, that is, one that lets one user damage another's mail or get access to unauthorized parts of the system.

In the kind of environment for which it was designed, with lots of bandwidth, qmail pumps out mail at a phenomenal rate. Dan Bernstein's original motivation for writing qmail was to get mailing list mail delivered fast, and it does that really well.

qmail has always struck me as complex to set up, but easier to manage in the long term. Is that a fair assessment?

It's not so much that it's complex to set up but that it's utterly different from sendmail. The basic configuration is pretty simple, but it's in a bunch of separate files rather than the barococo majesty of sendmail.cf.

The other problem in setting up qmail is due to its peculiar license that doesn't permit people to redistribute modified versions, so you have to pick up the original 1998 code and patch it to add new stuff. Fortunately, earlier this year several members of the qmail community put together netqmail, which combines qmail with a set of widely used patches and it's all you need.

Spam and UBE are obviously big headaches for managers today. What features does qmail support to help combat this?

Nothing built in, but just about every anti-spam scheme you ever heard of is available as a qmail add-on. Dan offers a program called rbldnsd that uses DNS blocklists like the SBL, and people add spam filters such as procmail, greylists, you name it. qmail's modular structure makes it easy to splice new features in.

Do you think there is a solution to spam, or is it something we'll all just have to live with?

There's certainly no magic bullet, but I think that combinations of technical and legal measures will eventually get it under control, although never make it completely go away.

You're a long-time author, well known for a large number of titles and the Internet Gurus group. Can I ask you how you manage the mountains of e-mail you must receive?

It's all standard Unix tools. I use procmail to sort my mail, Pine to read it, and I put most of the mailing lists to local newsgroups so I can read them with trn.

qmail handles a dizzying array of potential delivery and mail routing options. What's the best way to approach a new installation?

Start with a basic installation, then figure out what extra stuff you need. The configuration is mostly driven out of text files so it's easy enough to add new bits to your configuration. You'll also find that once you get some experience with qmail, what you want to add will be more evident.

Migration from an existing setup seems even more complicated. Is there some way of easing the migration from sendmail or postfix?

 Well, there is a chapter in my book on it. You have to figure out what your current setup is doing, then run down the list and make qmail do all the things you care about. I've often found that old sendmail setups have mountains of cruft, and you can throw a lot of it away when you see what your mail system is really doing.

You cover both IMAP and POP in your book. Which do you recommend?

Depends on your usual connection. If it's on a LAN or broadband, IMAP rocks, particularly if you're using one of the Maildir-based IMAP servers (Courier or binc) that supports multiple simultaneous sessions. I can have Pine on my BSD box, Thunderbird on my PC, and Web mail all open at once, and it just works, all viewing the same mailboxes.

On the other hand, if you do dialup, you're still better off with POP since IMAP can be painfully slow over a slow connection.

Could you tell us what we can expect to see from you next?

Internet for Dummies, fabulous all new 10th edition coming next summer.

About John R. Levine

John R. Levine writes, speaks, and consults on the Internet, electronic mail, cybersecurity, and related topics (www.johnlevine.com).

More Stories By Martin C. Brown

Martin C. Brown is a former IT director with experience in cross-platform integration. A keen developer, he has produced dynamic sites for blue-chip customers, including HP and Oracle, and is the technical director of Foodware.net. Now a freelance writer and consultant, MC, as he is better known, works closely with Microsoft as an SME; has a regular column on both ServerWatch.com and IBM's DeveloperWorks Grid Computing site; is a core member of the AnswerSquad.com team; and has written books such as XML Processing with Perl, Python and PHP, and the Microsoft IIS 6 Delta Guide.

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