Mail from Yandex does not reach. What could be the Exim configuration error?

Question

Exim

The problem was noticed only when receiving mail sent to several recipients using smtp.yandex.ru. When sending from the web interface, the problem is not observed.
The bottom line is that when sending from the Yandex web interface, Exim (4.86) receives during the SMTP session the number of RCPT TO commands corresponding to the number of recipients. And when sending via smtp.yandex.ru, there is only one RCPT TO command and only one recipient receives the letter. However, the To, Cc, and Bcc headers are ignored by Exim. Is this behavior normal? If not, what could be causing the headers to not be parsed? Exim configuration is close to default.
An example of an SMTP session in Exim when sending a letter via imap.yandex.ru:

16:10:51 17342 SMTP>> 220 mail.mydomain.com ESMTP Exim 4.86 Thu, 04 Feb 2016 16:10:51 +0300
16:10:51 17342 SMTP<< EHLO forward20m.cmail.yandex.net
16:10:51 17342 SMTP>> 250-mail.mydomain.com Hello forward20m.cmail.yandex.net [5.255.216.151]
16:10:51 17342 SMTP<< STARTTLS
16:10:51 17342 SMTP>> 220 TLS go ahead
16:10:51 17342 SMTP<< EHLO forward20m.cmail.yandex.net
16:10:51 17342 SMTP>> 250-mail.mydomain.com Hello forward20m.cmail.yandex.net [5.255.216.151]
16:10:51 17342 SMTP<< MAIL FROM:<[email protected]> SIZE=1556
16:10:51 17342 SMTP>> 250 OK
16:10:51 17342 SMTP<< RCPT TO:<[email protected]>
16:10:52 17342 SMTP>> 250 Accepted
16:10:52 17342 SMTP<< DATA
16:10:52 17342 SMTP>> 354 Enter message, ending with "." on a line by itself
16:10:52 17342 SMTP>> 250 OK id=1aRJgS-0004Vi-2b
16:10:52 17342 SMTP<< QUIT
16:10:52 17342 SMTP>> 221 mail.mydomain.com closing connection
16:10:52 17342 &#160;&#160;SMTP connection from forward20m.cmail.yandex.net [5.255.216.151] closed by QUIT

And the headers of the received email:

Return-path: <[email protected]>
Envelope-to: [email protected]
Delivery-date: Thu, 04 Feb 2016 16:10:52 +0300
Received: from forward20m.cmail.yandex.net ([5.255.216.151])
    by mail.mydomain.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256)
    (Exim 4.86 (FreeBSD))
    (envelope-from <[email protected]>)
    id 1aRJgS-0004Vi-2b
    for [email protected]; Thu, 04 Feb 2016 16:10:52 +0300
Received: from smtp1m.mail.yandex.net (smtp1m.mail.yandex.net [77.88.61.132])
    by forward20m.cmail.yandex.net (Yandex) with ESMTP id 71C0B21311
    for <[email protected]>; Thu,  4 Feb 2016 16:10:51 +0300 (MSK)
Received: from smtp1m.mail.yandex.net (localhost [127.0.0.1])
    by smtp1m.mail.yandex.net (Yandex) with ESMTP id 2632667405AF
    for <[email protected]>; Thu,  4 Feb 2016 16:10:51 +0300 (MSK)
Received: by smtp1m.mail.yandex.net (nwsmtp/Yandex) with ESMTPSA id 1KJiF8h9Lr-AoLKl8SV;
    Thu,  4 Feb 2016 16:10:50 +0300
    (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits))
    (Client certificate not present)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex.ru; s=mail; t=1454591450;
    bh=Sg0pwcVasB4JWlAUGR8ByMcGWNeZkme1J/Lilu4AzMs=;
    h=To:From:Subject:Message-ID:Date:User-Agent:MIME-Version:
     Content-Type:Content-Transfer-Encoding;
    b=MQgQbzBSGa/e0Rjya/A3GzcZBboNgdMgGX8yaZ8U8WzGKH667zXn+HzYG9IpwolaU
     Z2CLA07fzHvZ3IeWxtplRS2ZlwDWMvR96zEL3MUwOq/LxSv1n6pzOaP/HS/GYJ6Ab5
     XOs7rA2S0vTDOcrz2U8ehhHj3M3xv1/3k2C9JTBY=
Authentication-Results: smtp1m.mail.yandex.net; dkim=pass [email protected]
To: [email protected], [email protected]
From: <[email protected]>
Subject: TEST
Message-ID: <[email protected]>
Date: Thu, 4 Feb 2016 16:11:24 +0300
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101
 Thunderbird/38.5.0
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit

Answer 1

Headers of the letter and real recipients of the letter are not the same thing. The real recipients are determined not by the headers, but by the SMTP envelope (i.e. RCPT TO: in the session). Moreover, if in one letter, for example, there is 1 address in To, 2 addresses in CC and 3 addresses in BCC, then there will be 6 recipients. The BCC header in the received letter will not be present at all. The sending server can, at its discretion, send a letter in one session by issuing 6 RCPT TO: commands, or in different sessions, for example, 6 sessions for one recipient.
At the same time, if the same address is used in different headers (for example, in To and in CC), the letter, as a rule, arrives only once.