Add emails to a mailing queue instead of sending immediately to speed up sending forms for the website visitor and lower server load.

binmaocom

This plugin adds emails to a mailing queue instead of sending immediately. This speeds up sending forms for the website visitor and lowers the server load. 
Emails are stored in database which are deleted after emails are sent.
You can send all outgoing emails via an SMTP server or (the WordPress standard) PHP function <a href="http://php.net/manual/en/function.mail.php" rel="nofollow ugc">mail</a>, and either use <a href="https://codex.wordpress.org/Function_Reference/wp_cron" rel="nofollow ugc">wp_cron</a> or a cronjob (if your server/hoster supports this) to process the queue.
Plugin requires PHP 5.4 or above.

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