Answers.Body: <p>I found the answer on this other question: <a href="https://civicrm.stackexchange.com/questions/14954/mail-not-send-if-preferred-mail-format-is-null">Mail not send if preferred_mail_format is NULL</a>.</p>
  
  <p>The original problem seems reported and solved first on <a href="https://issues.civicrm.org/jira/browse/CRM-18037" rel="nofollow noreferrer">CRM-18037</a>. But also persist and dragged in later versions as reported on <a href="https://issues.civicrm.org/jira/browse/CRM-18157" rel="nofollow noreferrer">CRM-18157</a>, <a href="https://issues.civicrm.org/jira/browse/CRM-19135" rel="nofollow noreferrer">CRM-19135</a>, <a href="https://issues.civicrm.org/jira/browse/CRM-19442" rel="nofollow noreferrer">CRM-19442</a>, <a href="https://issues.civicrm.org/jira/browse/CRM-19423" rel="nofollow noreferrer">CRM-19423</a>.</p>
  
  <p>Otherwise in the latest fixes upgrade scripts that converts 'NULL' <code>preferred_mail_formats</code> to 'Both' are not executed. If I'm on right, last  time is executed is in <a href="https://github.com/civicrm/civicrm-core/blob/master/CRM/Upgrade/Incremental/sql/4.7.7.mysql.tpl#L61" rel="nofollow noreferrer">4.7.7 upgrade</a>.</p>
  
  <p>Meanwhile to solve current inconsistencies it seems suficient to execute the following script on the database:</p>
  
  <p><code>UPDATE `civicrm_contact` SET `preferred_mail_format` = 'Both' WHERE `preferred_mail_format` IS NULL;</code></p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-11-24T21:29:05.650Z
Answers.Text: https://issues.civicrm.org/jira/browse/CRM-19685
Answers.UserDisplayName: Francesc Bassas i Bullich
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-11-23T19:41:53.707Z
Answers.LastActivityDate: 2016-11-23T19:41:53.707Z
Answers.LastEditDate: 2017-04-13T12:53:13.167Z
Answers.UserDisplayName: Francesc Bassas i Bullich
Answers.Body: <p>This has been fixed for 4.7.15</p>
  
  <p>PR <a href="https://github.com/civicrm/civicrm-core/pull/9463" rel="nofollow noreferrer">https://github.com/civicrm/civicrm-core/pull/9463</a></p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-11-30T08:11:15.797Z
Answers.LastActivityDate: 2016-11-30T08:11:15.797Z
Answers.UserDisplayName: Yashodha Chaku
Body: <p>Since the 4.7.8 update to 4.7.10 and 4.7.10 to 4.7.12 recently some mails are not reaching their recipients. If I look at the Mailing Detail Report the Successful Deliveries rate is between 90% and 100% and the status of the not received mails are "Unknown".</p>
  
  <p>To see these mails on the report I have to filter as status "-any-" because there is no possibility to do it with the status "unknown".</p>
  
  <p>Has anyone encountered the same problem? What may be due?</p>
  
  <p><strong>Edit</strong></p>
  
  <p>I investigated a little more and I see that "Unknown" status appears when there is no record on the civicrm_mailing_event_bounce table AND when there is no record on the civicrm_mailing_event_delivered. Then, it seems that for some users, there isn't registering the delivery of the mail.</p>
  
  <p><del>I begin to suspect that the problem is related with an issue of inconsitency caches of the mailing recipients groups.</del></p>
  
  <p><strong>Edit 2</strong></p>
  
  <p>I found on logs messages like <code>[info] CiviMail will not send an empty mail body, Skipping: xxxxxxxxxx@xxxxx.xxx</code> corresponding to the contacts with mailing status marked as "Unknown".</p>
  
Tags: <civimail>
Title: Unknown mailing status on few mailings recipients
ThreadText: # Unknown mailing status on few mailings recipients
  
  (Asked by: username_0 on 2016-10-13)
  
  Since the 4.7.8 update to 4.7.10 and 4.7.10 to 4.7.12 recently some mails are not reaching their recipients. If I look at the Mailing Detail Report the Successful Deliveries rate is between 90% and 100% and the status of the not received mails are "Unknown".
  
  To see these mails on the report I have to filter as status "-any-" because there is no possibility to do it with the status "unknown".
  
  Has anyone encountered the same problem? What may be due?
  
  **Edit**
  
  I investigated a little more and I see that "Unknown" status appears when there is no record on the civicrm\_mailing\_event\_bounce table AND when there is no record on the civicrm\_mailing\_event\_delivered. Then, it seems that for some users, there isn't registering the delivery of the mail.
  
  ~~I begin to suspect that the problem is related with an issue of inconsitency caches of the mailing recipients groups.~~
  
  **Edit 2**
  
  I found on logs messages like `[info] CiviMail will not send an empty mail body, Skipping: xxxxxxxxxx@xxxxx.xxx` corresponding to the contacts with mailing status marked as "Unknown".
  
  **Tags:** civimail
  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_1 on 2016-11-30. Score: 3 | Accepted answer
  
  This has been fixed for 4.7.15
  
  PR <https://github.com/civicrm/civicrm-core/pull/9463>
  
  
  ---
  
  ### Answer by username_0 on 2016-11-23. Score: 2
  
  I found the answer on this other question: [Mail not send if preferred\_mail\_format is NULL](https://civicrm.stackexchange.com/questions/14954/mail-not-send-if-preferred-mail-format-is-null).
  
  The original problem seems reported and solved first on [CRM-18037](https://issues.civicrm.org/jira/browse/CRM-18037). But also persist and dragged in later versions as reported on [CRM-18157](https://issues.civicrm.org/jira/browse/CRM-18157), [CRM-19135](https://issues.civicrm.org/jira/browse/CRM-19135), [CRM-19442](https://issues.civicrm.org/jira/browse/CRM-19442), [CRM-19423](https://issues.civicrm.org/jira/browse/CRM-19423).
  
  Otherwise in the latest fixes upgrade scripts that converts 'NULL' `preferred_mail_formats` to 'Both' are not executed. If I'm on right, last time is executed is in [4.7.7 upgrade](https://github.com/civicrm/civicrm-core/blob/master/CRM/Upgrade/Incremental/sql/4.7.7.mysql.tpl#L61).
  
  Meanwhile to solve current inconsistencies it seems suficient to execute the following script on the database:
  
  `UPDATE `civicrm_contact` SET `preferred_mail_format` = 'Both' WHERE `preferred_mail_format` IS NULL;`
  
  > **Comments:**
  > **username_0**: https://issues.civicrm.org/jira/browse/CRM-19685  
  
  ---
  
  