title: Couldn't figure out why the relaying is denied
body: <p>Below is what happened to one mail send from a drupal client.</p>
  
  <pre><code>$ grep 'B6693C0977' /var/log/maillog
  Jan 19 14:12:30 instance-1 postfix/pickup[19329]: B6693C0977: uid=0 from=&lt;admin@mailgun.domainA.com&gt;
  Jan 19 14:12:30 instance-1 postfix/cleanup[20035]: B6693C0977: message-id=&lt;20170119141230.B6693C0977@mail.instance-1.c.tw-pilot.internal&gt;
  Jan 19 14:12:30 instance-1 postfix/qmgr[19330]: B6693C0977: from=&lt;admin@mailgun.domainA.com&gt;, size=5681, nrcpt=1 (queue active)
  Jan 19 14:12:33 instance-1 postfix/smtp[20039]: B6693C0977:
  to=&lt;username@hotmail.com&gt;, relay=smtp.mailgun.org[52.41.19.62]:2525, delay=2.4, 
  delays=0.02/0.05/1.8/0.53, dsn=5.7.1, status=bounced (host smtp.mailgun.org
  [52.41.19.62] said: 550 5.7.1 **Relaying denied** (in reply to RCPT TO command))
  Jan 19 14:12:33 instance-1 postfix/bounce[20050]: B6693C0977: sender non-delivery notification: ABB94C0976
  Jan 19 14:12:33 instance-1 postfix/qmgr[19330]: B6693C0977: removed
  </code></pre>
  
  <p>Relevant excerpts from my <code>/etc/postfix/main.cf</code> are below</p>
  
  <pre><code># RELAYHOST SETTINGS
  smtp_tls_security_level = encrypt
  smtp_sasl_auth_enable = yes
  smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
  smtp_sasl_security_options = noanonymous
  sender_dependent_relayhost_maps = hash:/etc/postfix/relayhost_map
  </code></pre>
  
  <p>and from <code>/etc/postfix/sasl_passwd</code> is follows</p>
  
  <pre><code>@mailgun.domainA.com postmaster@mailgun.domainA.com:password
  </code></pre>
  
  <p>and from <code>/etc/postfix/relayhost_map</code> is follows</p>
  
  <pre><code>@mailgun.domainA.com [smtp.mailgun.org]:2525
  </code></pre>
  
  <p>The permissions of the <code>db</code> files are as follows</p>
  
  <pre><code># ls -lZ /etc/postfix/relayhost_map.db
  -rw-r-----. root postfix unconfined_u:object_r:postfix_etc_t:s0 /etc/postfix/relayhost_map.db
  # ls -lZ /etc/postfix/sasl_passwd.db 
  -rw-r-----. root postfix unconfined_u:object_r:postfix_etc_t:s0 /etc/postfix/sasl_passwd.db
  </code></pre>
  
  <p>The problem is</p>
  
  <ul>
  <li>Outbound mails are not going.</li>
  <li>No logs are shown in mailgun console.</li>
  </ul>
  
  <p>Any insight is appreciated</p>