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+This is the Postfix 3.1 (stable) release.
+
+The stable Postfix release is called postfix-3.1.x where 3=major
+release number, 1=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-3.2-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 2.11 or earlier, read RELEASE_NOTES-3.0
+before proceeding.
+
+Major changes - address verification safety
+-------------------------------------------
+
+[Feature 20151227] The new address_verify_pending_request_limit
+parameter introduces a safety limit for the number of address
+verification probes in the active queue. The default limit is 1/4
+of the active queue maximum size. The queue manager enforces the
+limit by tempfailing probe messages that exceed the limit. This
+design avoids dependencies on global counters that get out of sync
+after a process or system crash.
+
+Tempfailing verify requests is not as bad as one might think. The
+Postfix verify cache proactively updates active addresses weeks
+before they expire. The address_verify_pending_request_limit affects
+only unknown addresses, and inactive addresses that have expired
+from the address verify cache (by default, after 31 days).
+
+Major changes - json support
+----------------------------
+
+[Feature 20151129] Machine-readable, JSON-formatted queue listing
+with "postqueue -j" (no "mailq" equivalent). The output is a stream
+of JSON objects, one per queue file. To simplify parsing, each
+JSON object is formatted as one text line followed by one newline
+character. See the postqueue(1) manpage for a detailed description
+of the output format.
+
+Major changes - milter support
+------------------------------
+
+[Feature 20150523] The milter_macro_defaults feature provides an
+optional list of macro name=value pairs. These specify default
+values for Milter macros when no value is available from the SMTP
+session context.
+
+For example, with "milter_macro_defaults = auth_type=TLS", the
+Postfix SMTP server will send an auth_type of "TLS" to a Milter,
+unless the remote client authenticates with SASL.
+
+This feature was originally implemented for a submission service
+that may authenticate clients with a TLS certificate, without having
+to make changes to the code that implements TLS support.
+
+Major changes - output rate control
+-----------------------------------
+
+[Feature 20150710] Destination-independent delivery rate delay
+
+Support to enforce a destination-independent delay between email
+deliveries. The following example inserts 20 seconds of delay
+between all deliveries with the SMTP transport, limiting the delivery
+rate to at most three messages per minute.
+
+/etc/postfix/main.cf:
+ smtp_transport_rate_delay = 20s
+
+For details, see the description of default_transport_rate_delay
+and transport_transport_rate_delay in the postconf(5) manpage.
+
+Major changes - postscreen dnsbl
+--------------------------------
+
+[Feature 20150710] postscreen support for the TTL of DNSBL and DNSWL
+lookup results
+
+Historically, the default setting "postscreen_dnsbl_ttl = 1h" assumes
+that a "not found" result from a DNSBL server will be valid for one
+hour. This may have been adequate five years ago when postscreen
+was first implemented, but nowadays, that one hour can result in
+missed opportunities to block new spambots.
+
+To address this, postscreen now respects the TTL of DNSBL "not
+found" replies, as well as the TTL of DNSWL replies (both "found"
+and "not found"). The TTL for a "not found" reply is determined
+according to RFC 2308 (the TTL of an SOA record in the reply).
+
+Support for DNSBL or DNSWL reply TTL values is controlled by two
+configuration parameters:
+
+postscreen_dnsbl_min_ttl (default: 60 seconds).
+
+ This parameter specifies a minimum for the amount of time that
+ a DNSBL or DNSWL result will be cached in the postscreen_cache_map.
+ This prevents an excessive number of postscreen cache updates
+ when a DNSBL or DNSWL server specifies a very small reply TTL.
+
+postscreen_dnsbl_max_ttl (default: $postscreen_dnsbl_ttl or 1 hour)
+
+ This parameter specifies a maximum for the amount of time that
+ a DNSBL or DNSWL result will be cached in the postscreen_cache_map.
+ This prevents cache pollution when a DNSBL or DNSWL server
+ specifies a very large reply TTL.
+
+The postscreen_dnsbl_ttl parameter is now obsolete, and has become
+the default value for the new postscreen_dnsbl_max_ttl parameter.
+
+Major changes - sasl auth safety
+--------------------------------
+
+[Feature 20151031] New "smtpd_client_auth_rate_limit" feature, to
+enforce an optional rate limit on AUTH commands per SMTP client IP
+address. Similar to other smtpd_client_*_rate_limit features, this
+enforces a limit on the number of requests per $anvil_rate_time_unit.
+
+Major changes - smtpd policy
+----------------------------
+
+[Feature 20150913] New SMTPD policy service attribute "policy_context",
+with a corresponding "smtpd_policy_service_policy_context" configuration
+parameter. Originally, this was implemented to share the same SMTPD
+policy service endpoint among multiple check_policy_service clients.
+
+Major changes - tls
+-------------------
+
+[Feature 20160207] A new "postfix tls" command to quickly enable
+opportunistic TLS in the Postfix SMTP client or server, and to
+manage SMTP server keys and certificates, including certificate
+signing requests and TLSA DNS records for DANE. See the postfix-tls(1)
+manpage for a detailed description.
+
+[Feature 20160103] The Postfix SMTP client by default enables DANE
+policies when an MX host has a (DNSSEC) secure TLSA DNS record,
+even if the MX DNS record was obtained with insecure lookups. The
+existence of a secure TLSA record implies that the host wants to
+talk TLS and not plaintext. For details see the
+smtp_tls_dane_insecure_mx_policy configuration parameter.
+
+[Incompat 20150721] As of the middle of 2015, all supported Postfix
+releases no longer enable "export" grade ciphers for opportunistic
+TLS, and no longer use the deprecated SSLv2 and SSLv3 protocols for
+mandatory or opportunistic TLS.
+
+These changes are very unlikely to cause problems with server-to-server
+communication over the Internet, but they may result in interoperability
+problems with ancient client or server implementations on internal
+networks. To address this problem, you can revert the changes with:
+
+Postfix SMTP client settings:
+
+ lmtp_tls_ciphers = export
+ smtp_tls_ciphers = export
+ lmtp_tls_protocols = !SSLv2
+ smtp_tls_protocols = !SSLv2
+ lmtp_tls_mandatory_protocols = !SSLv2
+ smtp_tls_mandatory_protocols = !SSLv2
+
+Postfix SMTP server settings:
+
+ smtpd_tls_ciphers = export
+ smtpd_tls_protocols =
+ smtpd_tls_mandatory_protocols = !SSLv2
+
+These settings, if put in main.cf, affect all Postfix SMTP client
+or server communication, which may be undesirable. To be more
+selective, use "-o name=value" parameter overrides on specific
+services in master.cf. Execute the command "postfix reload" to make
+the changes effective.
+
+[Incompat 20150719] The default Diffie-Hellman non-export prime was
+updated from 1024 to 2048 bits, because SMTP clients are starting
+to reject TLS handshakes with primes smaller than 2048 bits.
+
+Historically, this prime size is not negotiable, and each site needs
+to determine which prime size works best for the majority of its
+clients. See FORWARD_SECRECY_README for some hints in the quick-start
+section.
+