Sendmail is the de-facto mail-handler. Sendmail is the grand-father of all MTAs. It was originally written by Eric Allman while he was at the University of California at Berkeley. Read more hot
Aeon is designed to connect your favourite console mail user agent with smtp server.
Anti-Spam SMTP Proxy
aims to create an open source platform-independent SMTP Proxy server which implements whitelists and Bayesian filtering to rid the planet of the blight of unsolicited email (UCE). UCE must be stopped at the SMTP server
BL4's SMTP server
BL4's SMTP server is an inbound only SMTP server. It currently uses hardcoded values for handling email. The SMTP server puts the incoming email into various text files.
intended to be a sendmail replacement for workstations. It is written in perl. Included are an RFC 822 parser (the most complete perl implementation AFAIK), a mail queuing system, an ESMTP client and Net::DNS by Michael Fuhr
Clement is an email server application. Its main function is to block unwanted mail (spam) as soon as possible in the email exchange process
Courier is a fully functional SMTP/IMAP/POP3/HTTP (webmail) server. Courier implements many SMTP extensions: DSN, PIPELINING, 8BITMIME, and others. Courier also implements several new SMTP extensions for mailing list management and spam filtering. Read more
DBMail is a group of programs that enable the possiblilty of storing and retrieving mail messages from a (mysql) database. Read more
a mail server supporting IMAP and SMTP that uses a PostgreSQL database to store messages. Mailboxes are defined using SQL queries, allowing complex client-independent automatic message filtering and categorisation
Decimail Server is a mail server supporting IMAP and SMTP that uses a PostgreSQL database to store messages. Mailboxes are defined using SQL queries, allowing complex client-independent automatic message filtering and categorisation. For example you can partition your messages chronologically, by correspondent and by mailing list at the same time with each message appearing in several mailboxes. There is also the potential for fast keyword searching and to link with address book applications. Decimail also features anti-spam processing of outgoing messages.
a dictionary for the mailer postfix. This dictionary is able to get all virtual users out of a postgres database
scans incoming emails for bad file types, filenames, and virii using procmail
eProxy, is an SMTP proxy server framework specially designed for use in conjunction with Postfix version 2.1 and higher. However, it does also work as a frontend proxy however security wise I trust on the postfix smtpd.
Exim is a message transfer agent (MTA) developed at the University of Cambridge for use on Unix systems. Read more
fakehermes is a small, lightweight fake SMTP server. It's useful as a way to avoid spam by configuring your domains to point their secondary SMTP server to a fakehermes server.
an outgoing mail processor. It goes between the MUA (Mail User Agent) and the MTA (Mail Transport Agent), and can perform on the fly various sorts of processing and conversion on the outgoing mail in accord with the sender's specified rules, based on a highly configurable regular expressions system
an advanced qmail distribution based on qmail-sql which has SMTP, SMTPS, POP3, POP3S, IMAP, IMAPS services, antivirus and antispam filters, spoofing protections, SMTP AUTH support, SMTP-after-POP/IMAP, PHP5 API and much more
hermes is a generic, transparent and multi-platform anti-spam SMTP proxy that uses a combination of techniques (like greylisting, throttling, DNS white/blacklisting, SPF, etc.) to stop spam from reaching your mailbox. Many mailboxes see a 98% spam reduction with no false positives, as hermes is not filtering email based on content, but on strict adherence to the SMTP standards. It's also compatible with most SMTP extensions like STARTTLS (for SSL security) and SMTP-AUTH (for user authentication).
InfinyMail is an ODMR (RFC 2645) implementation, consisting of client and server. The client request its mail to the provider (ISP's MTA) via ODMR protocol.
Inflex is a two-stage sendmail system that gives you the ability to block or pass email based on any set of tests you choose, varying from Virus scans to Email text content.
magic-smtpd is a drop in replacement for qmail-smtpd, and was originally designed to be part of the LinuxMagic Magic Mail Server. This opensource version has been released to allow o thers to benifit from it's anti-spam components, and valid user checking to reduce server loads, and spam volumes. It is designed to support stock qmail installations, qmail/vpopmail installations, as well as having database support.
Mail Avenger is a highly-configurable, MTA-independent SMTP server. It allows you to reject spam during mail transactions, before spooling messages in your local mail queue. You can specify site-wide default policies for filtering mail, but individual users can also craft their own policies by a highly-configurable, MTA-independent SMTP (simple mail transport protocol) server. It allows you to reject spam during mail transactions, before spooling messages in your local mail queue. You can specify site-wide default policies for filtering mail, but individual users can also craft their own policies by creating avenger scripts in their home directories
MEsmtpd is a small SMTP-Daemon written in Perl.
Mimicry is a mail post-postprocessor daemon. It is easy to extend since the actual processing gets done in plugins. Mail messages are received and sent with SMTP. Current functionality includes adding disclaimers to messages and compressing attachments on the fly.
No-Brainer SMTP: for people who just need a plain old SMTP outgoing delivery system
nullmailer is a sendmail/qmail/etc replacement MTA for hosts which relay to a fixed set of smart relays. It is designed to be simple to configure, secure, and easily extendable.
popwatcher is a daemon that maintains a list of hosts that are authorized to use your mailserver as an SMTP relay based on those hosts successfully authenticating to your POP mail server.
Postfix is a free open source mail transfer agent (MTA), a computer program for the routing and delivery of email. It is intended as a fast, easy-to-administer, and secure alternative to the widely-used Sendmail MTA. Read more
Postoffice is a simple SMTP mail server and client. It provides a greylist to slow down the rate of incoming spam, and can be configured to do antivirus checking on incoming mail either via the sendmail milter protocol or a traditional hardcoded AV program.
postprox is an SMTP proxy which copies an SMTP conversation between its input and another SMTP server, but spools the DATA portion to a temporary file and runs a specified program on it before passing it on to the output server - or outputting an SMTP error code instead if the content filter says so.
Proto Balance Mail
(commercial) Proto Balance Mail is an enterprise SMTP cluster solution that supports distribution of email accounts. It scales up to 1,000,000 mailboxes apportioned over up to 125 backend mail servers (8000 mailboxes per server).
a flexible tool that allows you to reject, change or log email based on arbitrary critera. It accepts SMTP connections and forwards the SMTP commands and responses to another SMTP server. The 'DATA' email body is intercepted and filtered before forwarding
qmail is a modern replacement for sendmail. qmail uses the Simple Mail Transfer Protocol (SMTP) to exchange messages with MTA's on other systems. Read more
a filter that can be inserted in the qmail incoming mail path. It was designed to be simple and easy to install. Its main purpose was to filter any email with executable visual basic extensions
qpsmtpd is a qmail-smtpd replacement written in perl. The new features over the normal qmail-smtpd are primarily tools to avoid accepting mails we have to bounce anyway and a object oriented system for easily writing extension plugins.
RH Email Server
uses OpenLDAP authentication
for IMAP, POP3, SMTP, and SSL/TLS protocols. It
includes a Web interface, administration, and filters
sendmail X is a modularized message transfer system consisting of five (or more) persistent processes, all of which are multi-threaded except for one. A central queue manager controls SMTP servers and SMTP clients to receive and send e-mails, an address resolver provides lookups in various maps including DNS for mail routing, and a main control program starts the others processes and watches over their execution.
an implementation of an Electronic Mail Transport Agent, i.e. a program used for sending and receiving electronic mail, for Unix-like (POSIX compatible) systems. Smail-3 not only speaks SMTP, but can also gateway to other mail systems using transport protocols such as UUCP. Smail-3 is designed to be mostly compatible with sendmail but it uses a much simpler, cleaner, and hopefully more human friendly, configuration style than does sendmail
a SMTP-after-POP daemon for systems running Postfix with vm-pop3d, ipop3d or both
smtp_wrapper is a daemon program that acts as an SMTP proxy for Unix-like systems. smtp_wrapper supports SMTP filtering of spam.
smtpd is a lightweight mail server which sole purpose is to receive incoming messages and deliver it to local users. Its main "feature" (or non-feature, really) is to be completely unable to relay messages to adjacent servers: if an incoming message is not addressed to a local mailbox, smtpd will reject it. Another convenient feature is its ease of configuration: creating mailboxes or aliases boils down to simple filesystem operations (mkdir, symbolic links, etc.).
smtpproxy is an application level gateway for SMTP. Features are optional ETRN support, POP3 before SMTP with pop3proxy, mail path removal, restrictions on allowed senders and recipients.
smtptrapd is a high performance, multi-threaded daemon that provides an RFC 2821 compliant SMTP service that always returns a 4xx soft error to the RCPT TO verb. This is useful to run as a secondary MX service to reduce the amount of spam received.
V Mail Server
a small SMTP Server designed for home or small business use. It is very easy to use and was designed with Virus and Spam checking in mind
vchkpw is a collection of programs to automate creation and maintence of virtual domain email and pop accounts for qmail installations. It works with qmailadmin and sqwebmail.
a package of programs designed to manage multiple domains of mail addresses and mailboxes on a single host. It co-operates with qmail for mail delivery and program control
Vorpal Mail is intended as a more user-friendly (or should that be admin-friendly) replacement for the standard sendmail package. It's aims are to provide all the features that are required of a modern mail server, without all the complexity caused by sendmail's rules based configuration file.
vPostMaster is a Postfix mail server which integrates the best Open Source virus and spam filtering, and email server policy. Its features include: greylisting, SPF, per-user filtering rules, per-domain policy defaults, easy yum installation and configuration, spam and virus filtering, and can be administered through a web browser.
eXtended Account Managing Software: able to manage e-mail accounts for several domains and sites
Fast, rock stable, secure, GPL, feature filled and multiplatform ESMTP/POP3/FINGER/POPSYNC server
XMail Queue Manager
XMail Queue Manager gives you full control over the multi level nested mail queue of the server. You can track messages in their different states (sending, resending, frozen). Statistics tell you about the number of spooled messages. Its crossplatform remote feature allows you to manage queues of servers without GUI.
Z1 SecureMail Gateway
(commercial) a central, server-based software solution which provides encryption and digital signatures for the entire email traffic of an organization
a SMTP MTA which supplies all facilities needed at large scale messaging applications