Postfix

Postfix is an open source and free command-line software project implemented in C and designed from the ground up to act as a mailer server for GNU/Linux and UNIX-like operating systems. It is engineered as a Sendmail alternative.

Offers attractive junk mail control features

Junk mail control features include support for the Sendmail Milter (mail filter) protocol, stress-dependent configuration, postscreen zombie blocker, Greylisting plugin, address probing callout, access control per recipient, sender or client, SPF plugin, content filter, DNS whitelist support, as well as SMTP server per-client concurrency and rate limits.

Supports a wide range of protocols

The software supports a wide range of protocols, among which we can mention IPv6, TLS (Transport Layer Security), SMTP (Simple Mail Transfer Protocol), LMTP (Local Mail Transfer Protocol), QMQP (Quick Mail Queueing Protocol), SASL (Simple Authentication and Security Layer), and ETRN (Extended SMTP).

Supported databases and mailboxes

Postfix offers support for several databases, including LMDB database, Memcache database, CDB database, PostgreSQL database, SQLite database, Postfix 1.0 LDAP database, Berkeley DB database, MySQL database, as well as DBM database. In addition, it comes with support for various mailboxes, including the widely used mailbox and maildir formats, and virtual domains.

Supports sender-dependent SMTP relay and SASL password lookup

Among other features, we can mention support for VERP envelope return addresses, masquerading addresses in outbound SMTP mail, selective address rewriting, non-repeating queue IDs, sender-dependent SMTP relay and SASL password lookup, customizable delivery status notification message text, and server reject "footer" text.

Supported operating systems

Postfix is a true cross-platform project that has been successfully tested on a wide range of POSIX operating systems, such as GNU/Linux, BSD, Solaris, AIX, HP-UX, IRIX, Mac OS X and Tru64 UNIX. It is compatible with both 32-bit and 64-bit CPU architectures and it is successfully used on numerous hosting services.

What is new in this release:

• Improved before-queue content filter performance. With "smtpd_proxy_options = speed_adjust", the Postfix SMTP server receives the entire message before it connects to a before-queue content filter. Typically, this allows Postfix to handle the same mail load with fewer content filter processes.
• Improved address verification performance. The verify database is now persistent by default, and it is automatically cleaned periodically. Under overload conditions, the Postfix SMTP server no longer waits up to 6 seconds for an address probe to complete.
• Support for reputation management based on the local SMTP client IP address. This is typically implemented with "FILTER transportname:" actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values.
• The postscreen daemon (a zombie-blocker in front of Postfix) is still too rough for a stable release, and will be made "mature" in the Postfix 2.8 development cycle (however you can use Postfix 2.7 with the Postfix 2.8 postscreen and dnsblog executables and master.cf configuration; this code has already proven itself).

What is new in version :

• Improved before-queue content filter performance. With "smtpd_proxy_options = speed_adjust", the Postfix SMTP server receives the entire message before it connects to a before-queue content filter. Typically, this allows Postfix to handle the same mail load with fewer content filter processes.
• Improved address verification performance. The verify database is now persistent by default, and it is automatically cleaned periodically. Under overload conditions, the Postfix SMTP server no longer waits up to 6 seconds for an address probe to complete.
• Support for reputation management based on the local SMTP client IP address. This is typically implemented with "FILTER transportname:" actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values.
• The postscreen daemon (a zombie-blocker in front of Postfix) is still too rough for a stable release, and will be made "mature" in the Postfix 2.8 development cycle (however you can use Postfix 2.7 with the Postfix 2.8 postscreen and dnsblog executables and master.cf configuration; this code has already proven itself).

What is new in version 3.2.2:

• Improved before-queue content filter performance. With "smtpd_proxy_options = speed_adjust", the Postfix SMTP server receives the entire message before it connects to a before-queue content filter. Typically, this allows Postfix to handle the same mail load with fewer content filter processes.
• Improved address verification performance. The verify database is now persistent by default, and it is automatically cleaned periodically. Under overload conditions, the Postfix SMTP server no longer waits up to 6 seconds for an address probe to complete.
• Support for reputation management based on the local SMTP client IP address. This is typically implemented with "FILTER transportname:" actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values.
• The postscreen daemon (a zombie-blocker in front of Postfix) is still too rough for a stable release, and will be made "mature" in the Postfix 2.8 development cycle (however you can use Postfix 2.7 with the Postfix 2.8 postscreen and dnsblog executables and master.cf configuration; this code has already proven itself).

What is new in version 3.2.0:

• Improved before-queue content filter performance. With "smtpd_proxy_options = speed_adjust", the Postfix SMTP server receives the entire message before it connects to a before-queue content filter. Typically, this allows Postfix to handle the same mail load with fewer content filter processes.
• Improved address verification performance. The verify database is now persistent by default, and it is automatically cleaned periodically. Under overload conditions, the Postfix SMTP server no longer waits up to 6 seconds for an address probe to complete.
• Support for reputation management based on the local SMTP client IP address. This is typically implemented with "FILTER transportname:" actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values.
• The postscreen daemon (a zombie-blocker in front of Postfix) is still too rough for a stable release, and will be made "mature" in the Postfix 2.8 development cycle (however you can use Postfix 2.7 with the Postfix 2.8 postscreen and dnsblog executables and master.cf configuration; this code has already proven itself).

What is new in version 3.1.4:

• Improved before-queue content filter performance. With "smtpd_proxy_options = speed_adjust", the Postfix SMTP server receives the entire message before it connects to a before-queue content filter. Typically, this allows Postfix to handle the same mail load with fewer content filter processes.
• Improved address verification performance. The verify database is now persistent by default, and it is automatically cleaned periodically. Under overload conditions, the Postfix SMTP server no longer waits up to 6 seconds for an address probe to complete.
• Support for reputation management based on the local SMTP client IP address. This is typically implemented with "FILTER transportname:" actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values.
• The postscreen daemon (a zombie-blocker in front of Postfix) is still too rough for a stable release, and will be made "mature" in the Postfix 2.8 development cycle (however you can use Postfix 2.7 with the Postfix 2.8 postscreen and dnsblog executables and master.cf configuration; this code has already proven itself).

What is new in version 3.1.3:

• Improved before-queue content filter performance. With "smtpd_proxy_options = speed_adjust", the Postfix SMTP server receives the entire message before it connects to a before-queue content filter. Typically, this allows Postfix to handle the same mail load with fewer content filter processes.
• Improved address verification performance. The verify database is now persistent by default, and it is automatically cleaned periodically. Under overload conditions, the Postfix SMTP server no longer waits up to 6 seconds for an address probe to complete.
• Support for reputation management based on the local SMTP client IP address. This is typically implemented with "FILTER transportname:" actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values.
• The postscreen daemon (a zombie-blocker in front of Postfix) is still too rough for a stable release, and will be made "mature" in the Postfix 2.8 development cycle (however you can use Postfix 2.7 with the Postfix 2.8 postscreen and dnsblog executables and master.cf configuration; this code has already proven itself).

What is new in version 3.1.2:

• Improved before-queue content filter performance. With "smtpd_proxy_options = speed_adjust", the Postfix SMTP server receives the entire message before it connects to a before-queue content filter. Typically, this allows Postfix to handle the same mail load with fewer content filter processes.
• Improved address verification performance. The verify database is now persistent by default, and it is automatically cleaned periodically. Under overload conditions, the Postfix SMTP server no longer waits up to 6 seconds for an address probe to complete.
• Support for reputation management based on the local SMTP client IP address. This is typically implemented with "FILTER transportname:" actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values.
• The postscreen daemon (a zombie-blocker in front of Postfix) is still too rough for a stable release, and will be made "mature" in the Postfix 2.8 development cycle (however you can use Postfix 2.7 with the Postfix 2.8 postscreen and dnsblog executables and master.cf configuration; this code has already proven itself).

What is new in version 3.1.1:

• Improved before-queue content filter performance. With "smtpd_proxy_options = speed_adjust", the Postfix SMTP server receives the entire message before it connects to a before-queue content filter. Typically, this allows Postfix to handle the same mail load with fewer content filter processes.
• Improved address verification performance. The verify database is now persistent by default, and it is automatically cleaned periodically. Under overload conditions, the Postfix SMTP server no longer waits up to 6 seconds for an address probe to complete.
• Support for reputation management based on the local SMTP client IP address. This is typically implemented with "FILTER transportname:" actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values.
• The postscreen daemon (a zombie-blocker in front of Postfix) is still too rough for a stable release, and will be made "mature" in the Postfix 2.8 development cycle (however you can use Postfix 2.7 with the Postfix 2.8 postscreen and dnsblog executables and master.cf configuration; this code has already proven itself).

What is new in version 3.0.3:

• Improved before-queue content filter performance. With "smtpd_proxy_options = speed_adjust", the Postfix SMTP server receives the entire message before it connects to a before-queue content filter. Typically, this allows Postfix to handle the same mail load with fewer content filter processes.
• Improved address verification performance. The verify database is now persistent by default, and it is automatically cleaned periodically. Under overload conditions, the Postfix SMTP server no longer waits up to 6 seconds for an address probe to complete.
• Support for reputation management based on the local SMTP client IP address. This is typically implemented with "FILTER transportname:" actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values.
• The postscreen daemon (a zombie-blocker in front of Postfix) is still too rough for a stable release, and will be made "mature" in the Postfix 2.8 development cycle (however you can use Postfix 2.7 with the Postfix 2.8 postscreen and dnsblog executables and master.cf configuration; this code has already proven itself).

What is new in version 3.0.2:

• Improved before-queue content filter performance. With "smtpd_proxy_options = speed_adjust", the Postfix SMTP server receives the entire message before it connects to a before-queue content filter. Typically, this allows Postfix to handle the same mail load with fewer content filter processes.
• Improved address verification performance. The verify database is now persistent by default, and it is automatically cleaned periodically. Under overload conditions, the Postfix SMTP server no longer waits up to 6 seconds for an address probe to complete.
• Support for reputation management based on the local SMTP client IP address. This is typically implemented with "FILTER transportname:" actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values.
• The postscreen daemon (a zombie-blocker in front of Postfix) is still too rough for a stable release, and will be made "mature" in the Postfix 2.8 development cycle (however you can use Postfix 2.7 with the Postfix 2.8 postscreen and dnsblog executables and master.cf configuration; this code has already proven itself).

What is new in version 3.0.1:

• Improved before-queue content filter performance. With "smtpd_proxy_options = speed_adjust", the Postfix SMTP server receives the entire message before it connects to a before-queue content filter. Typically, this allows Postfix to handle the same mail load with fewer content filter processes.
• Improved address verification performance. The verify database is now persistent by default, and it is automatically cleaned periodically. Under overload conditions, the Postfix SMTP server no longer waits up to 6 seconds for an address probe to complete.
• Support for reputation management based on the local SMTP client IP address. This is typically implemented with "FILTER transportname:" actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values.
• The postscreen daemon (a zombie-blocker in front of Postfix) is still too rough for a stable release, and will be made "mature" in the Postfix 2.8 development cycle (however you can use Postfix 2.7 with the Postfix 2.8 postscreen and dnsblog executables and master.cf configuration; this code has already proven itself).

What is new in version 3.0.0:

• Improved before-queue content filter performance. With "smtpd_proxy_options = speed_adjust", the Postfix SMTP server receives the entire message before it connects to a before-queue content filter. Typically, this allows Postfix to handle the same mail load with fewer content filter processes.
• Improved address verification performance. The verify database is now persistent by default, and it is automatically cleaned periodically. Under overload conditions, the Postfix SMTP server no longer waits up to 6 seconds for an address probe to complete.
• Support for reputation management based on the local SMTP client IP address. This is typically implemented with "FILTER transportname:" actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values.
• The postscreen daemon (a zombie-blocker in front of Postfix) is still too rough for a stable release, and will be made "mature" in the Postfix 2.8 development cycle (however you can use Postfix 2.7 with the Postfix 2.8 postscreen and dnsblog executables and master.cf configuration; this code has already proven itself).

What is new in version 2.6.5:

• The Postfix Milter client would be out of step with a Milter application after the application sent a "quarantine" request at end-of-message time.
• The Milter application would still be in the end-of-message state, while Postfix would already be working on the next SMTP event, typically QUIT or MAIL FROM.
• In the latter case, Milter responses for the previously-received email message would be applied towards the next MAIL FROM transaction.
• The Postfix SMTP server would abort with an "unexpected lookup table" error when an SMTPD policy server was mis-configured in a particular way.

What is new in version 2.5.6:

• The SMTP server did not ask for a client certificate with "smtpd_tls_req_ccert = yes".
• Reduced TCP performance is avoided when reusing an SMTP connection with a larger than 4096-byte TCP MSS value.