Emails go to spam again?

Question

gmail

This is a very common problem, and yet no answer can be found. I am facing the problem for the second time, the first time I figured it out, but since then I have already forgotten how and I feel like a complete idiot.
Essence: a letter with a test text (an article from Yandex abstracts) is sent to a gmail address and falls into spam.
What exactly is:
- I'm sure that it's not a gmail account - I tried to send to other addresses
- no more than 10 letters were sent
- spf record v=spf1 ptr:oboi.ws ip4:94.242.7.203 a mx ~all
- the letter is sent from the server with a static ip (it is listed above)
- there is a reverse dns record on the ip corresponding to the domain
Headers of the letter that fell into spam after processing by Google:

Delivered-To: [email protected]<br/>
Received: by 10.229.94.144 with SMTP id z16cs208861qcm;<br/>
 Fri, 18 Mar 2011 08:46:24 -0700 (PDT)<br/>
Received: by 10.14.126.70 with SMTP id a46mr16266eei.180.1300463183158;<br/>
 Fri, 18 Mar 2011 08:46:23 -0700 (PDT)<br/>
Return-Path: &lt;[email protected]&gt;<br/>
Received: from oboi.ws (oboi.ws [94.242.7.203])<br/>
 by mx.google.com with ESMTP id q47si44684eeh.27.2011.03.18.08.46.21;<br/>
 Fri, 18 Mar 2011 08:46:22 -0700 (PDT)<br/>
Received-SPF: pass (google.com: domain of [email protected] designates 94.242.7.203 as permitted sender) client-ip=94.242.7.203;<br/>
Authentication-Results: mx.google.com; spf=pass (google.com: domain of [email protected] designates 94.242.7.203 as permitted sender) [email protected]<br/>
Date: Fri, 18 Mar 2011 18:46:20 +0300<br/>
Return-Path: [email protected]<br/>
To: [email protected]<br/>
From: =?UTF-8?B?0J7QsdC+0Lgud3M=?= &lt;[email protected]&gt;<br/>
Reply-to: =?UTF-8?B?0KLQtdGF0L3QuNGH0LXRgdC60LDRjyDQv9C+0LTQtNC10YDQttC60LAgb2Jv?=<br/>
 =?UTF-8?B?aS53cw==?= &lt;[email protected]&gt;<br/>
Subject: =?UTF-8?B?0J/QvtGH0YLQvtCy0YvQuSDRgtC10YHRgg==?=<br/>
Message-ID: &lt;[email protected]&gt;<br/>
X-Mailer: oboi.ws smtp<br/>
MIME-Version: 1.0<br/>
Content-Transfer-Encoding: base64<br/>
Content-Type: text/plain; charset=&quot;UTF-8&quot;<br/>
<br/>
0Jf...

Email headers sent by my smtp server:

Date: Fri, 18 Mar 2011 18:46:20 +0300<br/>
Return-Path: [email protected]<br/>
To: [email protected]<br/>
From: =?UTF-8?B?0J7QsdC+0Lgud3M=?= &lt;[email protected]&gt;<br/>
Reply-to: =?UTF-8?B?0KLQtdGF0L3QuNGH0LXRgdC60LDRjyDQv9C+0LTQtNC10YDQttC60LAgb2Jv?=<br/>
 =?UTF-8?B?aS53cw==?= &lt;[email protected]&gt;<br/>
Subject: =?UTF-8?B?0J/QvtGH0YLQvtCy0YvQuSDRgtC10YHRgg==?=<br/>
Message-ID: &lt;[email protected]&gt;<br/>
X-Mailer: oboi.ws smtp<br/>
MIME-Version: 1.0<br/>
Content-Transfer-Encoding: base64<br/>
Content-Type: text/plain; charset=&quot;UTF-8&quot;<br/>
<br/>
0Jf...

Answer 1

Read habrahabr.ru/blogs/sysadm/114852/ regarding DKIM. For

Answer 2

Hmm, well, given that the headers don't show anything suspicious, it's possible that the ip or address/domain was blacklisted, or Google just didn't like the content.