Let me say this is a rather cosmetic issue, but it appears with the latest commits (around 2.2.5 release) the scheme of 'Received' headers has changed for LMTP:
Inet socket: Return-Path: <dfn-adv-bounces@dfn-cert.de> Delivered-To: <tlx@leuxner.net> Received: from spectre.leuxner.net ([188.138.0.199]) by spectre.leuxner.net (Dovecot) with LMTP id 8AkXDF5cA1LvDgAAZ53dLw for <tlx@leuxner.net>; Thu, 08 Aug 2013 10:52:46 +0200
UNIX socket: Return-Path: <dfn-adv-bounces@dfn-cert.de> Delivered-To: <tlx@leuxner.net> Received: from spectre.leuxner.net ([]) by spectre.leuxner.net (Dovecot) with LMTP id q8WuGflcA1I3DwAAZ53dLw for <tlx@leuxner.net>; Thu, 08 Aug 2013 10:55:21 +0200
Old (Pre 2.2.5) build, UNIX socket: Return-Path: <dfn-adv-bounces@dfn-cert.de> Delivered-To: <tlx@leuxner.net> Received: from spectre.leuxner.net by spectre.leuxner.net (Dovecot) with LMTP id 8NiKKX0h+lFRIAAAZ53dLw for <tlx@leuxner.net>; Thu, 01 Aug 2013 10:51:09 +0200
While it probably should resolve the FQDN in 1) (Postfix does), not sure what it should do with a UNIX socket in 2). Previously as shown in 3) it had none of it...
Thomas