Отправка писем с сервера

Настраиваю отправку почты с VPS.

На сервере установлен PHPMailer, плюс установлен с дефолтными настройками sendmail.

На локальном компьютере почта отправляется (срабатывает установленный Papercut), на VPS не могу добиться получения почты адресатом.

PHPMailer уведомляет об отправке почты (с большой задержкой, до минуты ожидания работы скрипта), но реально почта не принимается сервером, где находится почтовый ящик (проверялся на gmail и др.)

php.ini - стоят дефолтные значения. Менял значения в hosts по совету отсюда и отсюда, но безрезультатно:

hosts

# nameserver config
# IPv4
127.0.0.1 localhost.localdomain localhost
1xx.xx.1.xxx  myhost.mysitename.com myhost       //добавленная строка, mysitename.com - подставляю адрес своего сайта
#1xx.xx.1.xxx  Debian-87-jessie-64-LAMP          //закомментированная дефолтная строка
#
# IPv6
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
xxxx:xxx:xxx:71::2  Debian-87-jessie-64-LAMP

var/log/mail.err

Mar 14 00:40:01 Debian-87-jessie-64-LAMP sm-msp-queue[15532]: My unqualified host name (Debian-87-jessie-64-LAMP) unknown; sleeping for retry
Mar 14 00:41:01 Debian-87-jessie-64-LAMP sm-msp-queue[15532]: unable to qualify my own domain name (Debian-87-jessie-64-LAMP) -- using short name

var/log/mail.log

Mar 14 00:24:02 Debian-87-jessie-64-LAMP sendmail[15272]: v2DNO2LK015272: from=www-data, size=1286, class=0, nrcpts=1, msgid=<da036d610926c6d3518dd53bc89fc6cc@mysitename.com>, relay=www-data@localhost
Mar 14 00:24:02 Debian-87-jessie-64-LAMP sm-mta[15308]: v2DNO2QA015308: from=<www-data@Debian-87-jessie-64-LAMP>, size=1470, class=0, nrcpts=1, msgid=<da036d610926c6d3518dd53bc89fc6cc@mysitename.com>, proto=ESMTP, daemon=MTA-v4, relay=localhost.localdomain [127.0.0.1]
Mar 14 00:24:02 Debian-87-jessie-64-LAMP sendmail[15272]: v2DNO2LK015272: to=post@emailbox.net, ctladdr=www-data (33/33), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=31286, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (v2DNO2QA015308 Message accepted for delivery)
Mar 14 00:24:02 Debian-87-jessie-64-LAMP sm-mta[15310]: v2DNO2QA015308: to=<post@emailbox.net>, ctladdr=<www-data@Debian-87-jessie-64-LAMP> (33/33), delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=121470, relay=mx5.emailbox.net. [xxx.xxx.116.118], dsn=4.3.0, stat=Deferred: 451 Unauthorised request. Try again later
Mar 14 00:24:03 Debian-87-jessie-64-LAMP sm-mta[15310]: v2DNO2QA015308: to=<post@emailbox.net>, ctladdr=<www-data@Debian-87-jessie-64-LAMP> (33/33), delay=00:00:01, xdelay=00:00:01, mailer=esmtp, pri=121470, relay=mx6.emailbox.net. [xxx.xxx.116.118], dsn=4.3.0, stat=Deferred: 451 Unauthorised request. Try again later
Mar 14 00:24:03 Debian-87-jessie-64-LAMP sm-mta[15310]: STARTTLS=client, relay=mx8.emailbox.net., version=TLSv1/SSLv3, verify=FAIL, cipher=DHE-RSA-AES256-GCM-SHA384, bits=256/256
Mar 14 00:24:03 Debian-87-jessie-64-LAMP sm-mta[15310]: v2DNO2QA015308: to=<post@emailbox.net>, ctladdr=<www-data@Debian-87-jessie-64-LAMP> (33/33), delay=00:00:01, xdelay=00:00:01, mailer=esmtp, pri=121470, relay=mx8.emailbox.net. [xxx.xxx.119.6], dsn=4.3.0, stat=Deferred: 451 Unauthorised request. Try again later
Mar 14 00:24:04 Debian-87-jessie-64-LAMP sm-mta[15310]: STARTTLS=client, relay=mx7.emailbox.net., version=TLSv1/SSLv3, verify=FAIL, cipher=DHE-RSA-AES256-GCM-SHA384, bits=256/256
Mar 14 00:24:04 Debian-87-jessie-64-LAMP sm-mta[15310]: v2DNO2QA015308: to=<post@emailbox.net>, ctladdr=<www-data@Debian-87-jessie-64-LAMP> (33/33), delay=00:00:02, xdelay=00:00:02, mailer=esmtp, pri=121470, relay=mx7.emailbox.net. [xxx.xxx.119.6], dsn=4.3.0, stat=Deferred: 451 Unauthorised request. Try again later
Mar 14 00:24:05 Debian-87-jessie-64-LAMP sm-mta[15310]: STARTTLS=client, relay=mx9.emailbox.net., version=TLSv1/SSLv3, verify=FAIL, cipher=DHE-RSA-AES256-SHA, bits=256/256
Mar 14 00:24:05 Debian-87-jessie-64-LAMP sm-mta[15310]: v2DNO2QA015308: to=<post@emailbox.net>, ctladdr=<www-data@Debian-87-jessie-64-LAMP> (33/33), delay=00:00:03, xdelay=00:00:03, mailer=esmtp, pri=121470, relay=mx9.emailbox.net. [xxx.xxx.122.10], dsn=4.3.0, stat=Deferred: 451 Unauthorised request. Try again later
Mar 14 00:24:05 Debian-87-jessie-64-LAMP sm-mta[15310]: v2DNO2QA015308: to=<post@emailbox.net>, ctladdr=<www-data@Debian-87-jessie-64-LAMP> (33/33), delay=00:00:03, xdelay=00:00:03, mailer=esmtp, pri=121470, relay=mx2.emailbox.net. [xxx.xxx.68.122], dsn=5.1.1, stat=User unknown
Mar 14 00:24:05 Debian-87-jessie-64-LAMP sm-mta[15310]: v2DNO2QA015308: v2DNO5QA015310: DSN: User unknown
Mar 14 00:24:05 Debian-87-jessie-64-LAMP sm-mta[15310]: v2DNO5QA015310: to=<www-data@Debian-87-jessie-64-LAMP>, delay=00:00:00, xdelay=00:00:00, mailer=local, pri=30000, dsn=2.0.0, stat=Sent
Mar 14 00:40:01 Debian-87-jessie-64-LAMP sm-msp-queue[15532]: My unqualified host name (Debian-87-jessie-64-LAMP) unknown; sleeping for retry
Mar 14 00:41:01 Debian-87-jessie-64-LAMP sm-msp-queue[15532]: unable to qualify my own domain name (Debian-87-jessie-64-LAMP) -- using short name

UPD 0

После добавления в php.ini : sendmail_path='/usr/sbin/sendmail -i -t -f noreply@mysitename.com' в ответе от сервера указывается обратный адрес, но остаются сообщения вида My unqualified host name (Debian-87-jessie-64-LAMP) unknown; sleeping for retry и unable to qualify my own domain name (Debian-87-jessie-64-LAMP) -- using short name :

Mar 14 11:14:16 Debian-87-jessie-64-LAMP sendmail[25223]: My unqualified host name (Debian-87-jessie-64-LAMP) unknown; sleeping for retry
Mar 14 11:15:16 Debian-87-jessie-64-LAMP sendmail[25223]: unable to qualify my own domain name (Debian-87-jessie-64-LAMP) -- using short name
Mar 14 11:15:16 Debian-87-jessie-64-LAMP sendmail[25223]: My unqualified host name (Debian-87-jessie-64-LAMP) unknown; sleeping for retry
Mar 14 11:16:16 Debian-87-jessie-64-LAMP sendmail[25223]: unable to qualify my own domain name (Debian-87-jessie-64-LAMP) -- using short name
Mar 14 11:16:16 Debian-87-jessie-64-LAMP sendmail[25223]: v2EAFGDK025223: Authentication-Warning: Debian-87-jessie-64-LAMP: www-data set sender to noreply@mysitename.com using -f
Mar 14 11:16:16 Debian-87-jessie-64-LAMP sendmail[25223]: v2EAFGDK025223: from=noreply@mysitename.com, size=1331, class=0, nrcpts=1, msgid=<a2cf59b71547225765e4f1b21f5e6c21@mysitename.com>, relay=www-data@localhost
Mar 14 11:16:16 Debian-87-jessie-64-LAMP sm-mta[25263]: v2EAGG5M025263: from=<noreply@mysitename.com>, size=1580, class=0, nrcpts=1, msgid=<a2cf59b71547225765e4f1b21f5e6c21@mysitename.com>, proto=ESMTP, daemon=MTA-v4, relay=localhost.localdomain [127.0.0.1]
Mar 14 11:16:16 Debian-87-jessie-64-LAMP sendmail[25223]: v2EAFGDK025223: to=post@emailbox.net, ctladdr=noreply@mysitename.com (33/33), delay=00:01:00, xdelay=00:00:00, mailer=relay, pri=31331, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (v2EAGG5M025263 Message accepted for delivery)
Mar 14 11:16:16 Debian-87-jessie-64-LAMP sm-mta[25265]: v2EAGG5M025263: to=<post@emailbox.net>, delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=121580, relay=mx6.emailbox.net. [213.186.116.118], dsn=5.1.1, stat=User unknown
Mar 14 11:16:16 Debian-87-jessie-64-LAMP sm-mta[25265]: v2EAGG5M025263: v2EAGG5M025265: DSN: User unknown
Mar 14 11:16:16 Debian-87-jessie-64-LAMP sm-mta[25265]: v2EAGG5M025265: to=<noreply@mysitename.com>, delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=30000, relay=mysitename.com. [xx.xx.xx.xxx], dsn=4.0.0, stat=Deferred: Connection refused by mysitename.com.

UPD 1

Изменил значения в hosts следующим образом + закомментировал все, что относится к IP6:

# IPv4
127.0.0.1 localhost.localdomain localhost
1xx.xx.1.xxx  server.mysitename.com server

# IPv6
#::1     ip6-localhost ip6-loopback
#fe00::0 ip6-localnet
#ff00::0 ip6-mcastprefix
#ff02::1 ip6-allnodes
#ff02::2 ip6-allrouters
#ff02::3 ip6-allhosts
#xxxx:xxx:xxx:71::2  Debian-87-jessie-64-LAMP

Длительного ожидания работы скрипта нет, отправка почты происходит мгновенно, var/log/mail.err пуст. Но почта в почтовый ящик не приходит.

var/log/mail.log

Mar 14 13:14:55 Debian-87-jessie-64-LAMP sendmail[27044]: v2ECEt2w027044: Authentication-Warning: Debian-87-jessie-64-LAMP: www-data set sender to noreply@mysitename.com using -f
Mar 14 13:14:55 Debian-87-jessie-64-LAMP sendmail[27044]: v2ECEt2w027044: from=noreply@mysitename.com, size=1331, class=0, nrcpts=1, msgid=<b5ac7ee3dc2fa8327781333b98225964@mysitename.com>, relay=www-data@localhost
Mar 14 13:14:56 Debian-87-jessie-64-LAMP sm-mta[27045]: v2ECEtuk027045: from=<noreply@mysitename.com>, size=1580, class=0, nrcpts=1, msgid=<b5ac7ee3dc2fa8327781333b98225964@mysitename.com>, proto=ESMTP, daemon=MTA-v4, relay=localhost.localdomain [127.0.0.1]
Mar 14 13:14:56 Debian-87-jessie-64-LAMP sendmail[27044]: v2ECEt2w027044: to=post@emailbox.net, ctladdr=noreply@mysitename.com (33/33), delay=00:00:01, xdelay=00:00:01, mailer=relay, pri=31331, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (v2ECEtuk027045 Message accepted for delivery)
Mar 14 13:14:56 Debian-87-jessie-64-LAMP sm-mta[27047]: v2ECEtuk027045: to=<post@emailbox.net>, delay=00:00:01, xdelay=00:00:00, mailer=esmtp, pri=121580, relay=mx6.emailbox.net. [xx.xx.xxx.xxx], dsn=5.1.1, stat=User unknown
Mar 14 13:14:56 Debian-87-jessie-64-LAMP sm-mta[27047]: v2ECEtuk027045: v2ECEuuk027047: DSN: User unknown
Mar 14 13:14:56 Debian-87-jessie-64-LAMP sm-mta[27047]: v2ECEuuk027047: to=<noreply@mysitename.com>, delay=00:00:00, xdelay=00:00:00, mailer=esmtp, pri=30000, relay=mysitename.com. [xx.xx.xx.xxx], dsn=4.0.0, stat=Deferred: Connection refused by mysitename.com.

Код скрипта

$mailer = new FreakMailer();      
$mailer->isMail();
$mailer->FromName = 'mysitename.com';
$mailer->From = 'noreply@mysitename.com';        
$mailer->CharSet = "UTF-8" ;
$mailer->Subject = 'Завершение регистрации';
$mailer->Body    = $body;
$mailer->AltBody = $body;
$mailer->AddAddress($email);
if(!$mailer->Send()) {
  echo 'Mailer Error: ' . $mailer->ErrorInfo;
} else { 
  //  
}

Прошу совета, где искать проблему?