Free what is smtp server software for linux

Dwarf Mail Server is a full-featured mail server developed on the Java platform, implementing SMTP, POP3 and IMAP4rev1 protocols.
Dwarf Mail Server provides support for rich application message processing via pluggable mail filters and agents, as well as full handling of virtual domains for the SMTP/POP3/IMAP4 protocols, and is free of charge for the binary redistribution.
Since the server is based on the Dwarf framework, it also shares its common design principles and features - simplicity, high modularity and extensibility, authentication and authorization, XML-based configuration, logging and remote management.
Main features:
- ESMTP, POP3 and IMAP4rev1 implementation
- application logic layer provided by mail filters and agents
- virtual mail hosts in SMTP/POP3/IMAP4 server
- application-independent authentication and authorization
- sample JSP-based webmail interface
Dwarf Mail Server is targeted for both end users who are just looking for simple, secure and robust mail server as well as developers who need an extensible and powerful framework for application message processing.
For users with minimal requirements it can offer portability, simple configuration as well as strong security.
- Portability: several OS platforms are supported via the Java technology, including MS Windows, UNIX/Linux/BSD, MacOS X and others.
- Configuration: just 3 lines have to be changed to fire up a sample mail server and a few of them to run a full featured SMTP/POP3/IMAP4 server.
- Security: it uses Java Platform Security Architecture in combination with Java Authentication and Authorization Service (JAAS), as well as SSL/TLS for the secure communication.
Advanced or enterprise users can additionally appreciate performance scalability, multiple domain handling, enhanced security features and modular design easing to incorporate it to the existing infrastructure.
- Scalability: gaining from multithreaded design and dynamically adjustable allocation of resources.
- Multiple domains: server is able to handle multiple virtual domains in a single instance for all SMTP, POP and IMAP protocols.
- Enhanced security: includes subject-based permissions and access control lists for IMAP, SMTP relaying control rules, host-based filtering, SSL/TLS communication, basic anti-spam filtering, etc.
- Robustness: client/server network communication is by design separated from the resource-expensive application logic layer. The server implementation is based on the unparsed byte streams whenever possible, including its own and highly efficient MIME parser.
Dwarf Mail Server also appears to be a suitable platform for application development and customization. Its modular structure and lightweight API allows enhancing existing functionality or completely exchanging the certain part as a whole:
- Message processing: mail filters and agents provide an unique infrastructure for rich message processing.
- Mail queue: physical mail queue representation is abstracted by the API specification and may replaced by a custom implementation.
- Storage subsystem: physical data representation (i.e. messages, folders, configuration options, ACLs) is abstracted by API and may be replaced by a custom implementation based on filesystem, SQL database, etc.
- MIME parser: the parsing engine may be reimplemented for the top efficiency according to the currently used mail storage.
Dwarf Mail Sever has been tested with the most popular mail clients like MS Outlook, Mozilla, Thunderbird, Opera, Apple Mail, Becky!, Pegasus, Eudora, Pine, The Bat! and others.
Other features:
- multi-threaded server
- dynamically adjusted number of active threads
- server API for mail, user data and ACL storages
- robust SMTP server architecture with flexible queue design
- simultaneous deliveries to remote SMTP hosts
- transparent Delivery System Notification (DSN) mechanism
- support for shared mail folders
- fast and universal stream-oriented MIME parser
- runtime server configuration
- built-in SSL/TLS support
- full documentation with user guides and tutorials
- samples with source code

Streamnik Server project is an IPTV server based on the open codecs Ogg/Vorbis and Ogg/Theora. It can stream a number of different channels and is optimized to run on leased (virtual) servers. The program schedule is defined by an SQL database table and can be changed at runtime.

lisp-network-server is a simple framework for writing Common Lisp network applications.

lisp-network-server framework takes care of listening on the network, accepting the connection and starting a new thread with handler functions of your network aware application.

Messa is an instant messager client and server. The client has a curses interface and works on the console.

Messa project supports multilingual messages and private messages. The server supports monoprocess operation (without threads), the ability to choose the listening port, and the ability to run under the console.

Net::Server is an extensible, general Perl server engine.
SYNOPSIS
#!/usr/bin/perl -w -T
package MyPackage;
use Net::Server;
@ISA = qw(Net::Server);
sub process_request {
#...code...
}
MyPackage->run(port => 160);
exit;
Main features:
- Single Server Mode
- Inetd Server Mode
- Preforking Simple Mode (PreForkSimple)
- Preforking Managed Mode (PreFork)
- Forking Mode
- Multiplexing Mode using a single process
- Multi port accepts on Single, Preforking, and Forking modes
- Simultaneous accept/recv on tcp, udp, and unix sockets
- Safe signal handling in Fork/PreFork avoids perl signal trouble
- User customizable hooks
- Chroot ability after bind
- Change of user and group after bind
- Basic allow/deny access control
- Customized logging (choose Syslog, log_file, or STDERR)
- HUP able server (clean restarts via sig HUP)
- Dequeue ability in all Fork and PreFork modes.
- Taint clean
- Written in Perl
- Protection against buffer overflow
- Clean process flow
- Extensibility
Net::Server is an extensible, generic Perl server engine. Net::Server combines the good properties from Net::Daemon (0.34), NetServer::Generic (1.03), and Net::FTPServer (1.0), and also from various concepts in the Apache Webserver.
Net::Server attempts to be a generic server as in Net::Daemon and NetServer::Generic. It includes with it the ability to run as an inetd process (Net::Server::INET), a single connection server (Net::Server or Net::Server::Single), a forking server (Net::Server::Fork), a preforking server which maintains a constant number of preforked children (Net::Server::PreForkSimple), or as a managed preforking server which maintains the number of children based on server load (Net::Server::PreFork). In all but the inetd type, the server provides the ability to connect to one or to multiple server ports.
Net::Server uses ideologies of Net::FTPServer in order to provide extensibility. The additional server types are made possible via "personalities" or sub classes of the Net::Server. By moving the multiple types of servers out of the main Net::Server class, the Net::Server concept is easily extended to other types (in the near future, we would like to add a "Thread" personality).
Net::Server borrows several concepts from the Apache Webserver. Net::Server uses "hooks" to allow custom servers such as SMTP, HTTP, POP3, etc. to be layered over the base Net::Server class. In addition the Net::Server::PreFork class borrows concepts of min_start_servers, max_servers, and min_waiting servers.
Net::Server::PreFork also uses the concept of an flock serialized accept when accepting on multiple ports (PreFork can choose between flock, IPC::Semaphore, and pipe to control serialization).

ClamSMTP project is an SMTP filter that allows you to check for viruses using the ClamAV anti-virus software.
It accepts SMTP connections and forwards the SMTP commands and responses to another SMTP server. The DATA email body is intercepted and scanned before forwarding.
ClamSMTP aims to be lightweight, reliable, and simple rather than have a myriad of options. Its written in C without major dependencies. If you need more options then you could use something big like AMaViS which is written in PERL and can do almost anything.
I wrote this with the Postfix mail server in mind. Heres how to configure it as a Postfix Content Filter.
ClamSMTP can also be used as a transparent proxy to filter an entire networks SMTP traffic at the router.
Enhancements:
- Support has been removed for listening on ports under 1024.
- Support has been added for embedded NULLs in email data.
- Problems with not listening properly when in daemon mode have been fixed, as well as warnings when compiled with gcc 4.0.
- Empty addresses are handled properly in logs.
- This release will not let Exchange send its strange binary data through the proxy.
- More Solaris fixes.
- Email messages are not rejected when the server is overloaded or encounters errors, or when starting the filter command fails.

libESMTP is an SMTP client which manages posting (or submission of) electronic mail via a preconfigured Mail Transport Agent (MTA).
libESMTP library may be used as part of a Mail User Agent (MUA) or other program that must be able to post electronic mail but where mail functionality is not that programs primary purpose.
The availability of a reliable lightweight thread-safe SMTP client eases the task of coding for software authors thus improving the quality of the resulting code.
Main features:
- libESMTP supports many SMTP extensions, notably PIPELINING (RFC 2920), DSN (RFC 1891) and SASL authentication (RFC 2554). SMTP AUTH is implemented using a SASL client library integrated into libESMTP. Supported SASL mechanisms include CRAM-MD5 and NTLM.
- libESMTP is also efficient. Because it buffers all network traffic, when used in conjunction with a pipelining SMTP server libESMTP significantly increases network performance, especially on slow connections and those with high latency. Even without a pipelining server libESMTP offers significantly better performance than would be expected with a simple client.
- libESMTP is not designed to be used as part of a program that implements a Mail Transport Agent. This is not because the code is unsuitable for use in an MTA, in fact the protocol engine is significantly better than those in many MTAs. Rather, by eliminating the need for MX lookup and next-hop determination, the design of libESMTP is simplified; thus goals are made achievable. Besides, such features are undesirable in a program that is not an MTA, particularly if the client is behind a firewall which blocks access to port 25 on the Internet.
Enhancements:
- This release applies bugfixes and plugs some memory leaks.
- It also attends to a few autoconf-related issues.