OpenSMTPD

OpenSMTPD is a completely free, cross-platform and open source implementation of a server-side SMTP (Simple Mail Transfer Protocol) protocol, as defined by the RFC 5321 specification.

The OpenSMTPD software includes various extra extensions and allows regular systems to exchange email messages with other machines that understand the SMTP protocol. The project was created because of lack of good SMTP implementations.

Provides a reasonable and complete SMTP implementation

OpenSMTPD has been created from the ground up as a replacement for existing SMTP implementations, providing a reasonable and complete implementation of the SMTP protocol. It is part of the OpenBSD project.

However, this does not mean that it cannot be installed on Linux kernel-based operating systems. As a matter of fact, OpenSMTPD can be used on all GNU/Linux distributions, as well as on the OpenBSD operating system.

Getting started with OpenSMTPD

The project can be easily installed on any distribution of GNU/Linux. Just download the latest release from either its website or from Softoware, save the archive somewhere on your personal computer (preferably your Home directory), and uncompress it.

Open your favorite Terminal app and use the ‘cd’ command to navigate to the location where you’ve extracted the archive file (e.g. cd /home/softoware/opensmtpd-5.4.4p1). There, you must run the ‘./configure && make’ command to configure and compile the program.

Install OpenSMTPD system wide and make it available to all users on your operating system by running the ‘sudo make install’ command as a privileged user or the ‘make install’ command as root after a successful compilation process.

Like any other daemon software, you must be root to use it. Therefore, run the ‘sudo smptd -h’ command to view the usage message of the OpenSMTPD software and learn more about its command-line options and how to use it.

What is new in this release:

• Improved logging:
• logging format has changed to ease parsing and be less verbose
• multi-line responses are now logged
• Improved documentation:
• portions of man pages have been rewritten to clarify them
• more examples for common use-cases have been added
• format specifiers have been documented
• forward-only has been documented
• Improved TLS / crypto:
• privileges-separated RSA engine
• better cope with errors in opportunistic TLS
• ciphers and curves can now be selected
• pki/ca interface has been reworked to allow custom CA
• certificate verification code has been greatly simplified
• SNI code has been simplified too
• switched to 2048-bits DH params by default
• Assorted improvements:
• domain-append is now supported
• support for SMTP-level filtering of users-provided senders
• initial support for masquerading
• usernames no longer need to be restricted to MAX_LOG_NAME
• DSN can now be generated without content or with headers only
• better handle IPv6 addresses in relay via rules
• fix unnecessary long delays relaying from backup to primary MX
• fd-exhaustion detection has been simplified
• reworked enqueuer
• the +-tag uses .tag folder if it exists, Maildir otherwise
• maildir:/path is now a supported expansion for aliases
• Experimental:
• filters plumbing is now always enabled
• the filter API is now available, though considered experimental

What is new in version 5.4.4p1:

• Improved configuration file:
• removed last known ambiguity in grammar
• much simpler configuration for TLS-enabled hosts
• most parameters are now swappable in listen and accept rules
• conditions may be negated (ie: accept from ! ...)
• forward-only rules can be declared to impose ~/.forward files
• new "recipient" keyword allows accept rule to provide a whitelist
• sender and recipient tables accept wildcard in their domains
• /!\ configuration file must be edited with this new release ! /!\
• /!\ please refer to smtpd.conf(5) and use smtpd -nf smtpd.conf /!\
• /!\ to validate. /!\
• TLS generic improvements:
• support for TLS Perfect Forward Secrecy
• support for providing custom CA certificate
• MTA improvements:
• mta may now require remote hosts to present valid certificates
• always attempt TLS before falling back to plaintext
• always present certificate if one is available
• AUTH LOGIN now supported
• mta can now specify a EHLO-hostname when relaying
• SMTP server improvements:
• inet4-only and inet6-only listeners are now possible
• listeners may now hide the From part in a Received-line
• listeners may require clients to provide a valid certificate
• banner hostname can now be dynamically fetched from a table
• Queue improvements:
• Introduce an envelope cache in the queue to improve disk-IO pattern
• smtpctl(8) improvements:
• show relays: displays list of currently active relays
• show routes: displays status of routes currently known by smtpd
• show hosts: displays list of known remote MX
• show hoststats: display status of last delivery for active domains
• resume route: resumes route temporarily disable by the MTA
• pause/resume envelope: allows pausing individual envelopes
• pause/resume message: allows pausing individual messages
• encrypt: allows generating credentials suitable for authentication
• show message/envelope is now compression/encryption aware
• documentation:
• table(5) describes format for static, file and db backends
• sendmail(8) describes our "sendmail" interface
• Reduced memory-usage in both general and stressed cases
• OpenSMTPD now automagically upgrades queue if format changes !
• Support Qmail-like "sticky home"
• Support for authenticating users from a credentials table
• Introduce passwd(5) table backend for user and credentials lookup
• Expansion variables in ~/.forward now supports modifiers
• much more efficient scheduler !
• And a lot of minor bug-fixes and internal cleanup !
• Experimental:
• SQLite table backend
• LDAP table backend
• MySQL table backend
• Postgres table backend
• Portable:
• Completely reworked autotools layout
• Limitations:
• No filters support yet (we're almost there)
• No masquerading or address rewrite yet (we're almost there)