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 to transport=local This will usually be followed by logging for an actual delivery: postfix/local[pid]: queueid: to=, 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.