Postfix 3.1 was feature-frozen a week or so ago, and it will take another week or so to before it is ready as the next stable release.
This will be an incremental release, compared to the transition from 2.11 to 3.0. But it will still be worthwhile to update. - 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. - A new always-on address_verify_pending_request_limit feature introduces a safety limit for the number of address verification probes in the active queue. - Machine-readable, JSON-formatted queue listing with "postqueue -j". - New "smtpd_client_auth_rate_limit" feature, to enforce an optional rate limit on AUTH commands per SMTP client IP address. - Postscreen support for the TTL of DNSBL and DNSWL lookup results. The TTL for a "not found" reply is determined according to RFC 2308 (it uses the TTL of an SOA record in the reply). Plus some minor stuff. Wietse