CRM-9698 Email throttling

A lot of email servers have limitations on the amount of emails that can be processed per certain period of time. Mostly the limitations are set to use format "emails/second". With its current functionality, CiviCRM can easily violate such limits when a large number of emails are sent by the application.

We have discussed this issue in the following thread:

http://forum.civicrm.org/index.php?topic=23177.0

Below I am copying the patch suggested by my colleague Val:

File: CRM/Mailing/Config.php
-----------
/**

• How long (in micro seconds) should we wait in between each mail delivery? Setting this to 0 disables it.
  *
• @var int
  */
  public $mailThrottleTime = 120000;
  -----------

File: CRM/Admin/Form/Setting/Mail.php
-----------
$this->addElement('text','mailThrottleTime', ts('Mailer Throttle Time'));
-----------

File: templates/CRM/Admin/Form/Setting/Mail.tpl
-----------
<tr class="crm-mail-form-block-mailThrottleTime">
<td class="label">{$form.mailThrottleTime.label}</td><td>{$form.mailThrottleTime.html} <br />
<span class="description">

The time to (u)sleep in between each e-mail in micro seconds. Setting this above 0 allows you to control the rate at which e-mail messages are sent to the mail server, avoiding filling up the mail queue very quickly. Set to 0 to disable.

</span></td>
</tr>
-----------

File: CRM/Mailing/BAO/Job.php
-----------
// If we have enabled the Throttle option, this is the time to enforce it.
$config = CRM_Core_Config::singleton();
if($config->mailThrottleTime > 0)

-----------

We hope that you will take into consideration this patch and our concern that the current functionality of the application can cause a lot of issues to CiviCRM users.

We are looking forward to your reply.

Regards,

Dave
Siteground Technical Support Team