UNIX Sysadmin Resources – Electronic Mail

This content was originally created, collected, and maintained by Stokely Consulting.
As of May 2005, it is being hosted and maintained by Bill Bradford.

Spam and Virus Email Blocking:

alt.spam FAQ, also known as Figuring Out Fake E-Mail and Posts, gives very useful tips on how to find out where fake mail and posts came from, and what you can do about it.
CIAC Email Spamming Countermeasures from the Computer Incident Advisory Capability discusses the detection and prevention of Email spamming. Links to important filtering methodologies, dos and don’ts.
Fight Spam on the Internet! referenced by the CIAC advisory above, explains more about spam, why it’s bad, and what you can do about it. Links to practical tools to boycott spam by mail filtering your personal account, an entire site, and more.
Central Command, makers of Vexira Antivirus software for Unix and Windows email servers. Supports Linux, FreeBSD, OpenBSD, Windows. Free trial.
Foiling Spam with an Email Password System is an interesting paper/process which uses Procmail. Written by Professor Timo Salmi.
MAPS the Mail Abuse Prevention System. Information on how to stop relay mailings. Includes the MAPS Realtime Blackhole List, a system for creating intentional network outages to limit the transport of known unwanted mass email. Controversial, but interesting in these spamming times we live in.
Securence Email Filtering offers anti spam, antivirus software and internet filter software for business and consumers.
Singlefin provides e-mail protection services. The company offers spam filtering, anti-virus protection, attachment blocking, policy filtering, store and forwarding service, and detailed reporting.
SPAM Zapper offers industrial strength SPAM filtering for business, ISPs and Internet users. They also offer the ability to encrypt email and protect your login ID and password using SSH encryption for email over the Internet. Available on-site or via the company’s servers, with graphical reporting. Site has good free white papers on best practices, security, and unsafe file types for email.
SPEWS.org, SPAM Prevention Early Warning System, is a list of areas on the Internet which several system administrators, ISP postmasters, and other service providers have assembled and use to deny email and in some cases, all network traffic from the locations.

Unix Web Mail tools:

Emumail provides an assortment of customizable webmail, email, collaboration, and message delivery tools and services for Unix and Windows platforms. Uses advertising in its no-cost mode, or you can buy an unlimited license to remove the ads. Requires Perl and uses IMAP or POP.
Endymion MailMan is a web-based application that allows users to send and receive Internet email from any Internet-connected web browser. Endymion MailMan uses any existing POP3 mailbox and SMTP server. Runs on your web server, written in Perl5.
IMP (Internet Messaging Program) is written in PHP and provides webmail accss to IMAP and POP3 accounts. Imp is part of the HORDE project, so you will also need the HORDE module. Runs on at least Linux, Redhat, BSDI, AIX, SCO UnixWare, Solaris 2.6/2.7, Debian GNU/Linux.
Mail-Gear is a mail server for Solaris and NT. Content-management features, roaming users-friendly, POP3/SMTP, Web-browser capable. Free 5-user download. From UR-Labs.
mailspinner supports remote access to email from any device with a web browser. Server runs on at least Solaris SPARC, Solaris x86, and NT. From Nascent Technologies.
Mirapoint Internet Message Server appliance and Message Router products provide intelligent routing and content filtering. Web email commercial products.
NeoMail is a free, GPL’d web-based e-mail client that can be installed on any UNIX mail server that is also running a web server. It requires Perl 5, suidperl, and NO additional modules to run.
SquirrelMail is a free, standards-based webmail package written in PHP4. It includes built-in pure PHP support for the IMAP and SMTP protocols, and all pages render in pure HTML 4.0 (with no Javascript) for maximum compatibility across browsers. It has very few requirements and is very easy to configure and install. SquirrelMail has a all the functionality you would want from an email client, including strong MIME support, address books, and folder manipulation.
TWIG is a intranet/groupware tool and application framework. Written in PHP. Includes email (via IMAP), contact manager, scheduling, Usenet newsgroups, todo lists, bookmarks and more features are planned. Free GPL software.


The Sendmail Home Page has pointers to the latest release, Sendmail FAQ, compiling tips, and lots more. Sendmail, Inc. is a company formed to continue work on freeware sendmail and a commercial version with a GUI interface to help with configuration. Significant anti-spam features are in version 8.9.*.
Differences between Sun sendmail and Berkeley sendmail is extremely useful to Sun sysadms.
Managing Internet Mail: Setting up and trouble-shooting sendmail and DNS courses from Harker Systems. Also other useful and important sendmail info and tools at Harker System’s site. They offer very good and reasonably priced courses to help us all understand Sendmail and to more easily grapple with sendmail.cf. We’ve taken these courses and definately recommend them for all Sendmail Postmasters.
Hints about sendmail/email includes sendmail configuration, sources, FAQs, and how to refuse email from unwanted domains (one way to deal with spammers).

Sendmail milters: (mail filters)

Anthony Howe’s Sendmail milters: A growing collection of Sendmail milters written in C by Anthony Howe: milter-sender (call-back tests), milter-spamc (Sendmail-SpamAssassin interface), milter-date (RFC 2821 Date conformance checking), milter-7bit (RFC 2045 Content-Transfer-Encoding conformance), milter-ahead (a poor man’s LDAP).
milter.org has a wealth of discussion and announcements to help you use libmilter to process your mail.
milter.free.fr provides a list of all available milters, with great explanations of how to use milters.
Sendmail Resources includes a great list of Sendmail Essentials and Security Issues. FAQs, source code, tips, and patches. Compiled by Paul Caloca of MuyCool Communications, LLC.

Sendmail: Theory and Practice is a book by Paul Vixie and Fredrick Avolio. Published by Digital Press.

Other Unix Mail Servers:

CommuniGate Pro is a Unix Mail server. Supports MIME, IMAP, lots of security features, POP, HTTP, LDAP, ACAP, DNR. Runs on at least Solaris, NT, 95/98, Linux, MacOS, FreeBSD, BSDI, OSF1, AIX, IRIX, HP/UL, UnixWare. Free trial download. Feature rich. From Stalker Software Inc.
Cucipop is a freely distributable POP3 daemon. It’s reported to be a fast, small, and full RFC1939 implementation of the POP3 protocol. Supports APOP and UIDL authentication, BSD and SysV mailbox formats. Excellent mailbox locking, even across NFS.
Emumail provides an assortment of customizable webmail, email, collaboration, and message delivery tools and services for Unix and Windows platforms. Uses advertising in its no-cost mode, or you can buy an unlimited license to remove the ads. Requires Perl and uses IMAP or POP.
InterMail Post.Office messaging server is a high capacity, easy to administer sendmail replacement. Supports SMTP and POP3, list management, web-browser interfaces. Runs on many Unix versions and NT. Free trial download. From Software.Com.
PMDF from innosoft international, inc. is a commercial product which integrates different mail systems into a central mailhub. Works with PC mail systems, POP, IMAP, X.400, SMTP, MIME, pagers, printers, UUCP, mailing lists, and more. The server software runs on Solaris, Digital UNIX, and OpenVMS.
Postfix is a free alternative to sendmail. Postfix attempts to be fast, easy to administer, and secure, while being sendmail compatible.
Programs for remote mail service via POP or IMAP contains free software for POP clients, servers and utilities. IMAP and POP perl client libraries.
Qpopper free POP3 server and pop password server from Qualcomm.
qmail by Dan Bernstein, is a free sendmail replacement. qmail’s web page says the product is designed to be secure, reliable, efficient, simple, and supports host and user masquerading, virtual domains, and lots more. Many people have written utilities for it. It definately seems to be worth checking out. Commercial support is available.

Bulk email & list-serving software:

Majordomo is great freeware and in wide use. Written in Perl. Also see the great MajorCool administrative web front end to Majordomo.
bulk_mailer is a C program.
ecartis listserver/mailing list manager, formerly Listar.
ListProcessor freeware from bu.edu.
ListProcessor commercial product is based on the free package.
Mailman from GNU.
Sympa mailing list manager.

Unix Email Attachments:

How to mail attachments from a Unix system discusses command line and scripting methods, including metamail, mpack, MIME methods, and other email processing tools. Written by J. Kyle Tucker.
Sending files as mail attachments describes how to send email using shell scripts, file attachments with uuencode and MIME. Part of the excellent Heiner’s SHELLdorado.


Procmail and SmartList, written by S.R. van den Berg, are in wide use. They are available in source form from (at least) ftp.aist-nara.ac.jp, ftp.net.ohio-state.edu, and ftp.psg.com. Procmail can be used to create mail-servers, mailing lists, sort your incoming mail into separate folders/files (real convenient when subscribing to one or more mailing lists or for prioritising your mail), preprocess your mail, start any programs upon mail arrival (e.g. to generate different chimes on your workstation for different types of mail) or selectively forward certain incoming mail automatically to someone. Written in C. See the included program documentation for the procmail discussion groups.
Enhancing E-mail Security with Procmail – the E-Mail Sanitizer discusses email security filtering and gives Procmail rulesets.
Processing Mail with Procmail from Infinite Ink has more procmail pointers.
Procmail tips and Procmail code/routines from Jari Aalto.
Procmail FAQ includes links to lots of Procmail and SmartList resources.
Timo’s Procmail tips and recipes contains a lot of useful information.

Unix Email clients (Mail User Agents):

eMailman Unix/Linux mail clients is an excellent, extensive list of links to many mail clients.
Mulberry is a high-performance, scalable, and graphical internet mail client. It supports IMAP, SMTP, MIME, POP3, local accounts, full disconnected IMAP support, PGP, SSL, filtering and more. Runs on Mac OS X, Linux, Solaris, Windows. Also check out their Mulberry Administrator’s Toolkit. Low-priced with big volume discounts.
MUTT is a free, small and powerful text-based mail client for Unix. ELM-like, color support, message threading, MIME, POP3, PGP support, and more. Good MUTT FAQ.
Nexor Despatch is an email client for Sun Solaris. It works with Microsoft Exchange, and has a look and feel like Microsoft Outlook. Free evaluation download.
Pine Information Center contains the latest version of the Pine email tool, documentation, installation help, and discussion forum.
XFMail is an XForms-based GUI mail reader for Unix. Handles multiple IMAP and POP accounts, local mail spools. Integrates with PGP or GnuPG, threading, highly configurable, built-in filtering, MIME support. Source and ginaries freely available.

Everything else:

Hugh Sasse’s Electronic Mail Related Information Page is a great resource for all-things-email. Includes information on email clients, mailing lists, web access by email, and email administration, Internet Hoaxes. Well done by Hugh G. Sasse.
Exim is a freely-available message transfer agent for Unix. It is similar to Smail, but has more defenses against mail bombs and spam. Web page gives documentation, code, links to mailing lists about Exim. Developed at the University of Cambridge.
Fetchmail is a free, well-documented, remote-mail retreival and forwarding utility used over on-demand TCP/IP links (like SLIP or PPP). Supports POP, IMAP, ESMPT and ETRN. Retreives mail from remote servers and forwards it via SMTP. Lots of features.
IMAP4 Information Center at the University of Washington. Also, see the CMU Project Cyrus info for an IMAP server.
Trying to Hack SSL into Certain Services describes how to graft SSL support onto UW IMAP using SSLeay and stunnel. Written by Ken Weaverling.
MetaMail (look for mm* in the directory) is free software to convert any mail-reader to full MIME support. Allows you to configure external viewers for many formats, like image, audio, multipart mail, and arbitrary binary data. Uses a mailcap mechanism. See the MetaMail README.
MIME FAQ (comp.mail.mime FAQ), maintained by Jerry Sweet.
Mpack/Munpack are free utilities to encode and decode binary files in MIME mail messages, the equivalent of uudecode/binhex. Source for Unix, pc, OS/2, Mac, Amiga and Archimedes.