This is the Postfix 3.6 (experimental) release.

The stable Postfix release is called postfix-3.5.x where 3=major
release number, 5=minor release number, x=patchlevel.  The stable
release never changes except for patches that address bugs or
emergencies. Patches change the patchlevel and the release date.

New features are developed in snapshot releases. These are called
postfix-3.6-yyyymmdd where yyyymmdd is the release date (yyyy=year,
mm=month, dd=day).  Patches are never issued for snapshot releases;
instead, a new snapshot is released.

The mail_release_date configuration parameter (format: yyyymmdd)
specifies the release date of a stable release or snapshot release.

If you upgrade from Postfix 3.4 or earlier, read RELEASE_NOTES-3.5
before proceeding.

License change
---------------

This software is distributed with a dual license: in addition to the
historical IBM Public License 1.0, it is now also distributed with the
more recent Eclipse Public License 2.0. Recipients can choose to take
the software under the license of their choice. Those who are more
comfortable with the IPL can continue with that license.

Incompatible change with snapshot 20200531
==========================================

Postfix delivery agents now log an explicit record when delegating
delivery to a different Postfix delivery agent. 

For example, with "best_mx_transport = local", an SMTP delivery
agent will now log when a recipient will be delivered locally. This
makes the delegating delivery agent visible, where it would otherwise
have remained invisible, which would complicate troubleshooting.

  postfix/smtp[pid]: queueid: passing <recipient> to transport=local

This will usually be followed by logging for an actual delivery:

  postfix/local[pid]: queueid: to=<recipient>, relay=local, ...

Other examples: the local delivery agent defers mailbox delivery
through mailbox_transport or through fallback_transport.

Major changes with snapshot 20200509
====================================

The threadsafe resolver API (res_nxxx() calls) is now the default,
not because the API is threadsafe, but because new features are
being added there.

To build old style, build with:

    make makefiles CCARGS="-DNO_RES_NCALLS..."

This is also the default for systems that are known not to support
the threadsafe resolver API, such systems that use libc-musl.

Incompatible changes with snapshot 20200416
===========================================

Security: this release disables DANE support on Linux systems with
libc-musl, because libc-musl provides no indication whether DNS
responses are authentic. This broke DANE support without a clear
explanation.
