Почему выскакивает надпись, что почта не дошла, хотя адресат видит посыл?

Выскакивает все время одно и тоже:This is the mPOP.Fallback_MX program at host mx28.mail.ru.I'm sorry to have to inform you that your message could notbe delivered to one or more recipients. It's attached below.For further assistance, please send mail to <postmaster>If you do so, please include this problem report. You candelete your own text from the attached returned message.<forward-qkkcb4@sms.beemail.ru>: host sms.beemail.ru[217.118.84.56] said: 550 Requested action not taken: mailbox unavailable forward-qkkcb4@sms.beemail.ru (in reply to RCPT TO command)Reporting-MTA: dns; mx28.mail.ruX-mPOP-Fallback_MX-Queue-ID: 4935ED7AEBX-mPOP-Fallback_MX-Sender: rfc822; jury39-2006@mail.ruArrival-Date: Thu, 2 Nov 2006 22:57:57 +0300 (MSK)Final-Recipient: rfc822; forward-qkkcb4@sms.beemail.ruOriginal-Recipient: rfc822;forward-qkkcb4@sms.beemail.ruAction: failedStatus: 5.0.0Remote-MTA: dns; sms.beemail.ruDiagnostic-Code: smtp; 550 Requested action not taken: mailbox unavailable forward-qkkcb4@sms.beemail.ruReceived: from mx27.mail.ru (mx27.mail.ru [194.67.23.64])by mx28.mail.ru (mPOP.Fallback_MX) with ESMTP id 4935ED7AEBfor <forward-qkkcb4@sms.beemail.ru>; Thu, 2 Nov 2006 22:57:57 +0300 (MSK)Received: from mail by mx27.mail.ru with local id 1Gfih8-000Io4-00for forward-qkkcb4@sms.beemail.ru; Thu, 02 Nov 2006 22:57:46 +0300X-ResentFrom: <vk_fedorov@mail.ru>Received: from [217.168.78.94] (port=57162 helo=[127.0.0.1])by mx27.mail.ru with asmtp id 1Gfigp-000Hvw-00for vk_fedorov@mail.ru; Thu, 02 Nov 2006 22:57:27 +0300Message-ID: <454A4D95.5020703@mail.ru>Date: Thu, 02 Nov 2006 22:57:09 +0300From: =?KOI8-R?Q?=E0=D2=C9=CA?= <jury39-2006@mail.ru>User-Agent: Mozilla Thunderbird 1.0 (Windows/20041206)X-Accept-Language: ru-ru, ruMIME-Version: 1.0To: vk_fedorov@mail.ruSubject: =?KOI8-R?Q?=28=C2=C5=DA_=D4=C5=CD=D9=29?=Content-Type: multipart/mixed; boundary="------------020605010805050004020003"