Друзья, я не осиливаю понять суть проблемы.
Почтовые сервера mail.ru не принимают письма от моего exim с сообщением:

2014-04-01 11:34:40 1WUv5c-0008F7-4q SMTP error from remote mail server after end of data: host mxs.mail.ru [94.100.180.150]: 421 Please
try again later
2014-04-01 11:34:41 1WUv5c-0008F7-4q == YYY@mail.ru R=dnslookup T=remote_smtp defer (-46): SMTP error from remote mail server
after end of data: host mxs.mail.ru [217.69.139.150]: 421 Please try again later

Есть идеи, с чем это связано?

Гугл письма принимает, но с оговоркой

Received: from realbiker.ru??????????????????????????????????? (realbiker.ru. [144.76.174.115])
        by mx.google.com with ESMTPS id 43si27201125eer.327.2014.04.01.02.47.56
        for <XXX@gmail.com>
        (version=TLSv1 cipher=RC4-SHA bits=128/128);
        Tue, 01 Apr 2014 02:47:56 -0700 (PDT)
Received-SPF: softfail (google.com: best guess record for domain of transitioning toxaxyz@realbiker.ru does not designate 144.76.174.115 as permitted sender) client-ip=144.76.174.115;
Authentication-Results: mx.google.com;
       spf=softfail (google.com: best guess record for domain of transitioning toxaxyz@realbiker.ru does not designate 144.76.174.115 as permitted sender) smtp.mail=XXX@realbiker.ru;
       dkim=neutral (no key for signature) header.i=@realbiker.ru
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=realbiker.ru; s=mail;
  h=Message-ID:From:Date:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:To; bh=KwUFOVKsGx6kkB3v2FJSezFLt5vR/phZX3UaPJ4Kte4=;
  b=Kq7ccYk+thJeD79926gIfH7Y08JHcETo8iH5ZF5CjBIKhlSh1+cFxKGzTzNBbPmL8OVLdiI1OLLJYFAIL2LV1Q==;
Received: from admin by CentOS-64-64-minimal with local (Exim 4.72)
  (envelope-from <XXX@realbiker.ru>)
  id 1WUvIS-0000AZ-6l
  for toxarbk@gmail.com; Tue, 01 Apr 2014 11:47:56 +0200