Message-ID in e-Newsletter, problem with Gmail

I'm sending emails via Mandrill. But started to notice that Google refuses to verify the signature of letters (DKIM=fail).

Received-SPF: pass (google.com: domain of bounce-md_30614885.5553845e.v1-7b1ab1e2747f47c58a8faf2358855ef0@track.georgesoros.me designates 205.201.136.11 as permitted sender) client-ip=205.201.136.11;
Authentication-Results: mx.google.com;
       spf=pass (google.com: domain of bounce-md_30614885.5553845e.v1-7b1ab1e2747f47c58a8faf2358855ef0@track.georgesoros.me designates 205.201.136.11 as permitted sender) smtp.mail=bounce-md_30614885.5553845e.v1-7b1ab1e2747f47c58a8faf2358855ef0@track.georgesoros.me;
       dkim=fail header.i=@georgesoros.me;
       dmarc=pass (p=NONE dis=NONE) header.from=georgesoros.me
Message-ID: <555384a1.c812ec0a.4f91.6906SMTPIN_ADDED_BROKEN@mx.google.com>
X-Google-Original-Message-ID: Newsletters-1-23-7d080c35103fdb965e34dc1363abe3d6@georgesoros.me

Spoke with technical support (Mandrill), see in attachment.