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  39 March 1999
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 113 <br>
 114
 115
 116 <h1 align="center">
 117 Postfix and Mailman deliver enhanced e-mail security and performance
 118 </h1>
 119
 120 <h3 align="center">
 121 Learn how these new open source products can improve the way you manage mail
 122 </h3>
 123
 124 <blockquote>
 125 <strong>Summary</strong><br> Good news -- there are better ways to do e-mail.
 126  Cameron and Kathryn introduce two new open source mail products called Postfix
 127 and Mailman and explain how you can begin to use them in your own work.
 128 Find out what you need to get started with these interesting and rewarding
 129 technologies. <em>(2,500 words)</em>
 130
 131 </blockquote>
 132
 133 <strong>By Cameron Laird and Kathryn Soraiz</strong>
 134
 135 <p>
 136 </p><hr noshade="">
 137 <p>
 138 <!-- begin body text -->
 139
 140 <img width="40" height="29" align="left" src="sunworld-199903_files/W.gif" alt="W">hile e-mail is the most mature and most widely diffused Internet
 141 application, it hasn't stopped growing.  The last year alone has
 142 seen several exciting developments and announcements, even in the
 143 oldest and least "sexy" domains:  mail transfer agents and mailing
 144 list managers.
 145 </p><p>
 146 Keep in mind the fundamental architecture of e-mail processing:  At
 147 your desktop, you compose a message.  You use a mail user agent
 148 (MUA) as the user interface to pass your message, along with such
 149 other information as the address for which it's intended, to an
 150 e-mail server.  A mail transfer agent (MTA) on the server takes
 151 responsibility for figuring out how best to deliver your message (Is
 152 it local -- should it go through my LAN?  Is it external?  What
 153 server on the other end will receive it?).  Generally, it
 154 communicates with another MTA on the server used by your intended
 155 recipient.  Once the message has been received by that second MTA,
 156 it's available for your recipient's MUA to access it.
 157 </p><p>
 158 </p><p>
 159 <font size="+1"><strong>The MTA market</strong></font><br>
 160 Sendmail dominates the MTA market, as it has for the last 20 years.
 161 About two-thirds of all e-mail servers rely on this
 162 open source product.  Sendmail is far more reliable, flexible,
 163 and portable than most of the commercial products that attempt
 164 to compete with it, and the recent launch of the for-profit
 165 Sendmail Inc. seems to have only enhanced the vigor of this
 166 venerable no-cost creation.
 167 </p><p>
 168 Sendmail isn't perfect, though.  It's bulky, difficult, and
 169 has a history of security problems.  More precisely, it's in
 170 just the shape you'd expect of a product originally built for
 171 a much different computing environment, and it's been patched and
 172 rewritten during several computing generations.  Still, the Sendmail
 173 development team has achieved quite a feat in bringing it
 174 forward from the far more relaxed security traditions of two
 175 decades ago.
 176 </p><p>
 177 Wietse Venema has an alternative, though.  Venema, a security
 178 expert on the IBM Research staff, started fresh, and has
 179 produced Postfix, a drop-in replacement for Sendmail which promises
 180 to deliver e-mail more quickly, conveniently, and safely.
 181 </p><p>
 182 Postfix isn't Sendmail's only challenger.  Zmailer, Smail,
 183 qmail, Post.Office, exim, the Sun Internet Mail Server
 184 (SIMS), MMDF, CommuniGate, PMDF, Netscape Messaging Server,
 185 and a variety of other products offer specific benefits for
 186 Unix-hosted e-mail service.  Postfix is the newest of these,
 187 however, and worth a look.
 188 </p><p>
 189 </p><p>
 190 <font size="+1"><strong>Postfix's heritage</strong></font><br>
 191 Venema has a track record in secure computing.  He says his "claim
 192 to fame is largely based on the low incidence of error" in the
 193 systems he's written, including Security Administrator Tool for
 194 Analyzing Networks (SATAN) and TCP Wrapper.  In designing and
 195 implementing Postfix (which began life as VMailer and Secure Mailer;
 196 don't be confused by the name changes), Venema's goal was for it "to
 197 be fast, easy to administer, and hopefully secure, while at the same
 198 time being Sendmail-compatible enough to not upset your users."
 199 </p><p>
 200 <table align="right" cellpadding="5" border="0"><tbody><tr><td>
 201 <center>
 202 <img vspace="3" width="182" height="281" src="sunworld-199903_files/wietse-m64.jpg">
 203 <br><font size="-1"><strong>
 204 Wietse Venema
 205 </strong></font></center>
 206 </td></tr></tbody></table>
 207 </p><p>
 208 He's made enough progress toward that goal that IBM has agreed to
 209 release Postfix as an open source product under an IBM license in
 210 the spirit of Perl's Artistic License.  (Caution:  While IBM
 211 supports Venema, its marketing department occasionally garbles the
 212 message.  Don't be alarmed if you run into a Web page that suggests
 213 you must pay for Postfix, or that its use is otherwise
 214 restricted.  While IBM is arguably the big company that best
 215 understands the open source story, it's still learning.  The first
 216 official IBM Web pages about Postfix were confusing.)
 217 </p><p>
 218 Venema labels the current Postfix a "beta."  To him this means
 219 "something close to perfection... It has nothing to do with software
 220 quality."  He's quite confident in the quality of Postfix.  For him,
 221 beta releases amount to an experiment to determine users' needs.
 222 </p><p>
 223 Sendmail is a famous monolith:  it's one big program that does
 224 everything.  Postfix is more Unix-like in that it consists of a
 225 number of little programs, each of which is easy to understand and
 226 validate, including postlock, postalias, postlog, postmap, and
 227 others.  This is part of the answer to Sendmail's notorious
 228 vulnerability.  Because Sendmail does so much, it effectively needs
 229 superuser privileges and is correspondingly easy to subvert.  Each
 230 of Postfix's parts has a limited role, so even if it's faulty and
 231 behaves in an unplanned way, it's unlikely to have enough security
 232 permissions to do any serious damage.
 233 </p><p>
 234 </p><p>
 235 <font size="+1"><strong>Becoming a Postfix administrator</strong></font><br>
 236 Trying out Postfix for yourself is only a small commitment.  A
 237 compressed source code bundle (cryptographically authenticated, of
 238 course) is well under a megabyte. Once fully expanded, unpacked, and
 239 generated, a complete build tree, including all object files and
 240 binaries, fills from 30 to 50 megabytes, depending on the target
 241 operating system.  It's utterly straightforward to build a complete
 242 installation kit on every common Unix platform:  the
 243 <code>make</code> takes less than 10 minutes to run, even on poky
 244 hardware.  The INSTALL directions included thoroughly explain how to
 245 do one of the following:
 246 </p><p>
 247 </p><ul>
 248 <li>Send mail only, without changing an existing Sendmail installation
 249 </li><li>Send and receive mail via a virtual host interface, still without any change to an existing Sendmail installation
 250 </li><li>Replace Sendmail altogether
 251 </li></ul>
 252 <p>
 253 You might choose the first of these if your primary motivation is to
 254 improve the performance of bulk mailing.  This gives you a way to
 255 experiment and quantify the speed-up, while leaving everything
 256 you've already configured to handle incoming e-mail in place and
 257 unaltered.
 258 </p><p>
 259 Postfix seems to be less scary to manage than Sendmail.  Customizing
 260 or even configuring Sendmail always feels like <em>a big deal</em>;
 261 on the other hand, Postfix is quite a bit easier to experiment with
 262 because you can test just one thing at a time.  Venema, for example,
 263 recently added a "debugging" feature suggested by Bennett Todd, a
 264 Unix systems and security analyst working on Wall Street:  a
 265 "soft_bounce" selection to ensure that, even in the case of
 266 misconfiguration, messages are not erroneously returned to their
 267 senders.
 268 </p><p>
 269 Our speed tests were equivocal: While Postfix consistently was zippier
 270 for us, the results were so sensitive to configuration that anyone
 271 with serious performance requirements will need and want to run his
 272 or her own tests.  For the light loads the majority of hosts
 273 typically experience, performance enhancements can be
 274 invisible.  With very high traffic levels, though, whether inbound
 275 or outbound, Postfix (and such alternatives as qmail and
 276 Post.Office) handles a multiple of Sendmail's limits.
 277 </p><p>
 278 Both Sendmail's and Postfix's current releases run about 50,000 lines of
 279 source code.  Postfix has six times as many source files and they
 280 average, of course, only about a sixth the size of Sendmail
 281 sources.  That's the sort of thing that contributes to Postfix's
 282 approachability.  It's much easier to localize changes, problems,
 283 and opportunities in Postfix's sources.
 284 </p><p>
 285 <!-- break -->
 286 </p><p>
 287 </p><p>
 288 <font size="+1"><strong>Choosing an MTA</strong></font><br>
 289 Should you stay with Sendmail?  Try Postfix?  Test-drive a
 290 commercial alternative?  Here are the main elements we consider when
 291 deciding between these possibilities:
 292 </p><p>
 293 Sendmail has it all.  If you need features, Sendmail is likely to be
 294 the place they first appear and are exercised the most.  Sendmail
 295 has at least an order of magnitude more source-code hackers than any
 296 of the other MTAs.  Most Unix boxes ship with Sendmail.  Sendmail's
 297 the easy choice for most system administrators.
 298 </p><p>
 299 If you're using Sendmail, though, you have a professional
 300 responsibility to update it to a current release.  The security
 301 hazards of running an older version (some major Unix vendors still
 302 ship Sendmail 5.65!) are simply unacceptable.
 303 </p><p>
 304 It takes less than an hour to do a basic installation of Postfix.
 305 If you inherit a complicated and undocumented Sendmail.cf
 306 configuration, you might be tweaking your Postfix tables for a
 307 while; Postfix does <em>not</em> support Sendmail.cf.  Postfix's
 308 address-rewriting tables are easy enough to use, though, so that
 309 even starting from scratch shouldn't take you all day.  What you
 310 have after such an investment is a far safer MTA that will probably
 311 perform much better.
 312 </p><p>
 313 Anyone considering Postfix should also know about qmail -- a
 314 more mature open source project that occupies almost exactly the
 315 same niche as Postfix.  Its security and performance are very good,
 316 and it's had a couple more years to ripen than Postfix.  It has
 317 about the same set of features as Postfix, plus a clever built-in
 318 "aliasing" scheme that simplifies mailing list management.
 319 Postfix's configuration files are fewer and perhaps more readable
 320 than qmail's; choosing between their approaches seems to be a matter
 321 of personal taste.  Venema and qmail's inventor, Daniel J.
 322 Bernstein, have such strong personalities that some users decide
 323 between their products based on compatibility with their authors.
 324 Also, note that the qmail license is an unusual one.  While
 325 Bernstein has liberalized it again recently, it generally has been
 326 more restrictive than the licenses for many other open source
 327 products in that it restricts developers from modifying the core of
 328 qmail or distributing binary images.  This has been a predictably
 329 contentious topic throughout qmail's history.  On one side,
 330 Bernstein doesn't want people to degrade qmail's security, even if
 331 inadvertently, and give his product a bad name.  But then proponents
 332 of license liberalization argue that the license is a practical
 333 inconvenience that decreases the usefulness of qmail.
 334 </p><p>
 335 You're probably running Sendmail now, and all you need to do is pick
 336 up the latest release for its tighter security and antispamming
 337 features.  But do tens of thousands of people look to you when they
 338 have e-mail problems?  Is your domain a prominent one that might
 339 attract crackers?  Has your uptime been floating higher?  In such
 340 cases, it's time you at least begin to experiment with Postfix (or
 341 qmail, or one of the higher-end commercial products), which will
 342 give you superior performance and security to Sendmail with all the
 343 reliability that the latter has gained during two decades of
 344 refinement.
 345 </p><p>
 346 Finally, if you select or are leaning toward Postfix, strongly
 347 consider subscribing to the postfix-announce, postfix-users, and/or
 348 postfix-testers mailing lists.  The latter, in particular, is where
 349 the design of new features is properly discussed.  The Postfix home
 350 pages supplies more information about these mailing lists.
 351 </p><p>
 352 </p><p>
 353 <font size="+1"><strong>The Mailman arrives</strong></font><br>
 354 Another open source product released to beta just this winter
 355 is Mailman, the GNU Mailing List Manager.
 356 </p><p>
 357 <table align="left" cellpadding="5" border="0"><tbody><tr><td>
 358 <center>
 359 <img vspace="3" width="388" height="228" src="sunworld-199903_files/mailman.gif">
 360 <br><font size="-1"><strong>
 361 </strong></font></center>
 362 </td></tr></tbody></table>
 363 </p><p>
 364 The market for mailing list management systems (MLMSs) is
 365 reminiscent of that for MTAs:  While a plethora of products is
 366 available, Majordomo is freely available and has led the pack in
 367 popularity for many years.  But also like Sendmail, Majordomo now
 368 seems clumsy and difficult to manage.
 369 </p><p>
 370 Mailman has been designed for a Webified world.  All actions --
 371 subscription requests, list administration, management reports --
 372 can be performed either through a Web interface or more traditional
 373 textual commands.  Moreover, Mailman integrates archiving, digests,
 374 Usenet gateways, spam protection, and bulk mailing. Improved
 375 customization and filtering are planned after the first official
 376 release.
 377 </p><p>
 378 One reassuring aspect of Postfix and Mailman is that their creators
 379 use them.  Venema has depended on Postfix as the only MTA on his own
 380 node for over a year, while Ken Manheimer, John Viega, Scott Cotton,
 381 and Barry Warsaw developed Mailman largely as an extension of their
 382 own needs for more convenient and higher performing mailing list
 383 management than other products afford.  Among other
 384 responsibilities, Mailman keeps the mailing lists of all python.org
 385 activities, including the Python Special Interest Groups (Python
 386 SIGs), straight.
 387 </p><p>
 388 </p><p>
 389 <font size="+1"><strong>Performance primary</strong></font><br>
 390 Warsaw, a system engineer at the Corporation for National Research
 391 Initiatives, told us, "Performance was primary.  We used Majordomo
 392 before, and when a lot of messages came through, they just bogged
 393 the machine down.  We're really happy with how Mailman's working
 394 out."  The migration from Majordomo has been easy:  "It took five
 395 minutes to convert three mailing lists, purely through the Web
 396 interface."
 397 </p><p>
 398 According to Warsaw, Mailman is coded in approximately 13,000 lines
 399 of Python code, along with 600 lines of C which
 400 wrap security facilities.  Mailman exposes Python as an extension
 401 language that allows for customization of Mailman's interfaces.
 402 </p><p>
 403 Mailman further resembles Postfix in having a robust and swift
 404 generation.  Warning:  As a practical matter, you'll need root
 405 access on your host to configure Mailman properly.  Most open source
 406 products can be generated and initially tested by ordinary Unix
 407 users.  Some organizations have a policy that requires this.  With
 408 Mailman, though, you'll at least need to create a new account and
 409 group (the default for both is "mailman") for Mailman's use.
 410 </p><p>
 411 The distributions for both Postfix and Mailman have clearly written
 412 README files that point to details on licensing, installation
 413 procedures, and known problems.  Be careful.  Sometimes the
 414 documentation lags the application.  There have been a few cases
 415 where a fix appeared in a release, but the documentation didn't
 416 catch up until later.  In the worst case, this means that something
 417 works, but you can only scrutinize further by reading source or
 418 experimenting with the installation in getting Mailman to work
 419 in other environments.
 420 </p><p>
 421 Warsaw needs only a few words to explain his judgment of Mailman's
 422 progress:  "I'm biased, but I really see no reason to use Majordomo
 423 now.  Mailman's performance is that much better, it has more
 424 features, and it's just as reliable."  He's working on making the
 425 conversion from one to the other just as simple.  While migrating a
 426 Majordomo mailing list into Mailman is straightforward now, Warsaw
 427 intends to document and further automate it after the 1.0 release.
 428 </p><p>
 429 The final milestone before the Free Software Foundation releases
 430 Mailman as an official product is resolution of a couple of faults
 431 reported on Linux file systems that Mailman's core development team
 432 haven't yet reproduced.
 433 </p><p>
 434 </p><p>
 435 <font size="+1"><strong>Summary</strong></font><br>
 436 The software you're already using to handle your e-mail
 437 requirements probably works reliably.  However, the scale of
 438 your operations is likely growing, while security threats
 439 become more difficult, and your users' demands for convenience
 440 expand.  It might be time for you to move to a new technology --
 441 one better suited to modern needs.  Several of the best e-mail
 442 products are open source.  In particular, you can easily
 443 install Postfix and Mailman, and test their performance in
 444 realistic settings.  Postfix and Mailman already have healthy
 445 user communities.  You can have confidence that Postfix and
 446 Mailman will be fresh and well-supported for years to come.
 447
 448 <img height="8" width="8" src="sunworld-199903_files/dingbat.gif">
 449 <!-- end body text -->
 450
 451 <a name="endnote">
 452 </a></p><p>
 453 <a name="endnote"><em>Thanks to Bennett Todd for his candid discussions of MTAs.</em>
 454 </a>
 455
 456 </p><p>
 457 <a name="bio">
 458 </a><table cellpadding="0" cellspacing="3" border="0">
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 461 <!--IMG-->
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 463 <td bgcolor="#000000"><img src="sunworld-199903_files/dot_clear.gif" width="2" height="1" align="bottom" border="0"></td>
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 465 <strong>
 466 <font size="-1" face="Arial,Helvetica,Sans-serif">
 467 About the author
 468 </font>
 469 </strong><br>
 470 <a name="author" href="http://sunworld.com/sunworldonline/cgi-bin/swol-mailto.cgi?cameron.laird@sunworld.com+/swol-03-1999/swol-03-mailtools.html+author">Cameron Laird</a> and <a name="author" href="http://web.archive.org/web/20000614102509/http://sunworld.com/sunworldonline/cgi-bin/swol-mailto.cgi?kathryn.soraiz@sunworld.com+/swol-03-1999/swol-03-mailtools.html+author">Kathryn Soraiz</a> manage their own software consultancy, Network Engineered Solutions, from just outside Houston, TX. They write <em>SunWorld's</em> bi-weekly <strong><a href="http://web.archive.org/web/20000614102509/http://www.sunworld.com/sunworldonline/common/swol-backissues-columns.html#regex">Regular Expressions</a></strong> column.
 471
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 494 Features:
 495  </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-change.html"> - How to manage and implement change in your Unix environment
 496  </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-fibre-scsi.html"> - Fibre Channel vs. SCSI: Which is more advantageous for your Storage Area Network?
 497  </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-mailtools.html"> - Postfix and Mailman deliver enhanced e-mail security and performance
 498
 499 </option><option value="http://www.sunworld.com/sunworldonline/index.html">
 500 News &amp; Views:
 501 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-silicon.html"> - Silicon Carny: A lazy afternoon
 502 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-bookshelf.html"> - Man evolves to machine
 503 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-sco.html"> - SCO grasping at the Linux straw?
 504 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-jini.html"> - Anything to everything
 505 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-itarchitect.html"> - The physical data architecture
 506 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-newsbriefs.html"> - New Product Briefs (March 1, 1999)
 507 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-career.html"> -
 508 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-csl.html"> - Sun extends Community Source Licensing to chip architectures
 509 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-sunspots.html"> - The latest tidbits on Sun deals and product news
 510 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-if.html"> - The network is the story: News on the latest Internet standards and struggles
 511 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-letters.html"> -
 512 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-eyeoncomp.html"> - Up-to-the-minute news on Sun's rivals
 513 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-regex.html"> - Regular Expressions: Dylan's appeal
 514 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-linuxworld.html"> - LinuxWorld: IBM fills out Linux offerings
 515 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-newsbriefs2.html"> - New Product Briefs (March 1, 1999)
 516 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-msft.html"> - Microsoft touts E-commerce strategy
 517 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-linuxworld2.html"> - News from LinuxWorld Expo
 518 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-linuxworld2.html"> - Highlights from LinuxWorld Expo
 519 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-ossummit.html"> - Open source software braces for another big year
 520 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-sunlinux2.html"> - Sun licenses Java Media APIs to Linux developers
 521 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-sunlinux.html"> - Sun licenses Java Media APIs to Linux developers
 522 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-netdynamics.html"> - Sun unveils new application server strategy
 523 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-gates.html"> - Gates predicts NT's high-end success next year
 524 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-newsbriefs.html"> - New Product Briefs (March 1, 1999)
 525 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-java-japan.html"> - Sun, NTT DoCoMo team on Java, Jini
 526 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-java.html"> - Sun keeps its foot in Java's door
 527 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-xeon.html"> - Intel unveils Pentium III Xeon
 528 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-unixware.html"> - SCO dresses up UnixWare for the data center
 529 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-linuxcebit.html"> - CEBIT: Linux Alley Is crowded, but lacks apps
 530 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-server.html"> - IDC: Worldwide server revenues down in Q4/98, volume up
 531 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-aol.html"> - Sun, AOL form e-commerce "virtual company"
 532 </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-aol2.html"> - AOL reorganizes to fold in Netscape
 533
 534 </option><option value="http://www.sunworld.com/sunworldonline/index.html">
 535 Tech Expertise:
 536  </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-insidesolaris.html"> - The Solaris process model: Part 7
 537  </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-security.html"> - Do you have an Incident Response Procedure in place?
 538  </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-connectivity.html"> - Building a reliable NT server, part 3
 539  </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-perf.html"> - Sun's new compilers and tools
 540  </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-unix101.html"> - Using bc, the programmable calculator, Part 1
 541  </option><option value="http://www.sunworld.com/swol-03-1999/swol-03-supersys.html"> - A patch-work column, Part 2
 542
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 567 </tr>
 568 <tr>
 569 <td> </td>
 570 <td>
 571 <ul>
 572 <a name="resourcex"><li>Sendmail Consortium
 573 <br></li></a><a href="http://www.sendmail.org/">http://www.sendmail.org/</a><li>Sendmail Inc.
 574 <br><a href="http://www.sendmail.com/">http://www.sendmail.com/</a></li><li>The Postfix home page
 575 <br><a href="http://www.postfix.org/">http://www.postfix.org/</a></li><li>MTA survey
 576 <br><a href="ftp://koobera.math.uic.edu/www/surveys/smtpsoftware3.txt">ftp://koobera.math.uic.edu/www/surveys/smtpsoftware3.txt</a></li><li>"The original 'killer app'" (a <em>LinuxWorld-Tapping the Source</em>  feature on qmail)
 577 <br><a href="http://www.linuxworld.com/linuxworld/expo/lw-email.html">http://www.linuxworld.com/linuxworld/expo/lw-email.html</a></li><li>The Open Source page
 578 <br><a href="http://www.opensource.org">http://www.opensource.org</a></li><li>Mailman home page
 579 <br><a href="http://www.list.org/">http://www.list.org/</a></li><li>The GNU Project and the Free Software Foundation
 580 <br><a href="http://www.gnu.org">http://www.gnu.org</a></li><li>Wietse Venema's tools
 581 <br><a href="ftp://ftp.porcupine.org/pub/security/index.html">ftp://ftp.porcupine.org/pub/security/index.html</a></li><li>"Report from SANS '98: Why Wietse Venema says Sendmail can never be made secure" July 1998 <strong>Security</strong> column in <em>SunWorld</em>
 582 <br><a href="http://www.sunworld.com/swol-07-1998/swol-07-security.html">http://www.sunworld.com/swol-07-1998/swol-07-security.html</a></li><li>Majordomo FAQ
 583 <br><a href="http://www.greatcircle.com/majordomo/FAQ.html">http://www.greatcircle.com/majordomo/FAQ.html</a></li><li>Cameron Laird's personal notes on Python
 584 <br><a href="http://starbase.neosoft.com/%7Eclaird/comp.lang.python/python.html">http://starbase.neosoft.com/~claird/comp.lang.python/python.html</a></li></ul><strong>Other SunWorld resources</strong><ul><li>The <em>SunWorld</em> Topical Index -- a comprehensive listing of all <em>SunWorld</em> articles by subject
 585 <br><a href="http://www.sunworld.com/common/swol-siteindex.html">http://www.sunworld.com/common/swol-siteindex.html</a></li><li>sunWHERE -- launchpad to hundreds of online resources for Sun users
 586 <br><a href="http://www.sunworld.com/sunwhere.html">http://www.sunworld.com/sunwhere.html</a></li><li>Back issues of <em>SunWorld</em>
 587 <br><a href="http://www.sunworld.com/common/swol-backissues.html">http://www.sunworld.com/common/swol-backissues.html</a></li><li>IDG.net, your one-stop IT resource
 588 <br><a href="http://www.idg.net">http://www.idg.net</a>
 589 </li></ul>
 590 </td><td> </td>
 591 </tr>
 592 </tbody></table>
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