386BSD is a discontinued operating system based on the Berkeley Software Distribution (BSD) that was developed by couple Lynne and William Jolitz. Released on March 17, 1992, it was the first fully operational Unix operating system to be completely free and open source.
Fetchmail is an open-source software utility for POSIX-compliant operating systems which is used to retrieve e-mail from a remote POP3, IMAP, or ODMR mail server to the user's local system. It was developed from the popclient program, written by Carl Harris.
Sendmail is a general purpose internetwork email routing facility that supports many kinds of mail-transfer and delivery methods, including the Simple Mail Transfer Protocol (SMTP) used for email transport over the Internet.
The Maildir e-mail format is a common way of storing email messages in which each message is stored in a separate file with a unique name, and each mail folder is a file system directory. The local file system handles file locking as messages are added, moved and deleted. A major design goal of Maildir is to eliminate the need for program code to handle file locking and unlocking.
A message delivery agent (MDA), or mail delivery agent, is a computer software component that is responsible for the delivery of e-mail messages to a local recipient's mailbox. It is also called a local delivery agent (LDA).
procmail is an email server software component — specifically, a message delivery agent (MDA). It was one of the earliest mail filter programs. It is typically used in Unix-like mail systems, using the mbox and Maildir storage formats.
PF is a BSD licensed stateful packet filter, a central piece of software for firewalling. It is comparable to netfilter (iptables), ipfw, and ipfilter.
In Unix computing, Ion is a tiling and tabbing window manager for the X Window System. It is designed such that it is possible to manage windows using only a keyboard, without needing a mouse. It is the successor of PWM and is written by the same author, Tuomo Valkonen. Since the first release of Ion in the summer 2000, similar alternative window management ideas have begun to show in other new window managers: Larswm, ratpoison, StumpWM, wmii, xmonad and dwm.
Systrace is a computer security utility which limits an application's access to the system by enforcing access policies for system calls. This can mitigate the effects of buffer overflows and other security vulnerabilities. It was developed by Niels Provos and runs on various Unix-like operating systems.
IPFilter is an open-source software package that provides firewall services and network address translation (NAT) for many Unix-like operating systems. The author and software maintainer is Darren Reed. IPFilter supports both IPv4 and IPv6 protocols, and is a stateful firewall.
Filesystem in Userspace (FUSE) is a software interface for Unix and Unix-like computer operating systems that lets non-privileged users create their own file systems without editing kernel code. This is achieved by running file system code in user space while the FUSE module provides only a bridge to the actual kernel interfaces.
Postfix is a free and open-source mail transfer agent (MTA) that routes and delivers electronic mail.
getmail is a simple mail retrieval agent intended as a replacement for fetchmail, implemented in Python. It can retrieve mail from POP3, IMAP4, and Standard Dial-up POP3 Service servers, with or without SSL. It supports simple and domain (multidrop) mailboxes, mail filtering via any arbitrary program, and supports a wide variety of mail destination types, including mboxrd, maildir, and external arbitrary mail delivery agents. Unlike fetchmail, getmail's Python foundation makes it nearly immune to buffer overflow security holes. It also has a simpler configuration syntax than fetchmail, but supports fewer authentication protocols. The software can also function as a basic mail delivery agent.
The comparison of mail servers covers mail transfer agents (MTAs), mail delivery agents, and other computer software that provide e-mail services.
The Portable C Compiler is an early compiler for the C programming language written by Stephen C. Johnson of Bell Labs in the mid-1970s, based in part on ideas proposed by Alan Snyder in 1973, and "distributed as the C compiler by Bell Labs... with the blessing of Dennis Ritchie."
FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD). The first version of FreeBSD was released in 1993 developed from 386BSD and the current version runs on x86, ARM, PowerPC and RISC-V processors. The project is supported and promoted by the FreeBSD Foundation.
OpenBSD is a security-focused, free and open-source, Unix-like operating system based on the Berkeley Software Distribution (BSD). Theo de Raadt created OpenBSD in 1995 by forking NetBSD 1.0. The OpenBSD project emphasizes portability, standardization, correctness, proactive security, and integrated cryptography.
OpenSSH is a suite of secure networking utilities based on the Secure Shell (SSH) protocol, which provides a secure channel over an unsecured network in a client–server architecture.
Maildrop is a Mail delivery agent used by the Courier Mail Server. The maildrop Mail Delivery Agent (MDA) also includes filtering functionality.
