This plugin when activated automatically redirects all email sent through wp_mail/phpmailer to the user currently logged in or the site administrator.
The redirected email contains information about where the original email would have been sent to.
Use this plugin if you want to test email-sending features without actually sending emails our to anyone but yourself. I wrote this plugin to ease debugging with subscribe2.
Since Version 1.2 you can choose whether to redirect all email to the currently logged in user (default), the site administrator (only wpmu) or the blog administrator.

Mail Debug

Redirects all email sent through wordpress to the user currently logged in or the site administrator.

hildende

Birmania

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 as files 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.
Tools:
<ul>
<li>You can send test mails to test your setup.</li>
<li>You can process the mailing queue manually instead of waiting for cronjob.</li>
</ul>
Supervisors: 
* You can display basic informations about mail processing performances 
* You can display the mailing queue in the backend to see emails that will be sent with next processing. 
* You can display the invalid mails and delete or retry them. 
* You can display the sent mails and delete them.
Coming soon:
<ul>
<li>Storing mailing data in database instead of files.</li>
<li>Using plugin for SMTP mails without using mailing queue.</li>
</ul>
Feel free to suggest features or send feedback in the <a href="https://wordpress.org/support/plugin/smtp-mailing-queue" rel="ugc">support section</a>, via <a href="mailto:antoine.brultet@gmail.com" rel="nofollow ugc">email</a> or by creating a pull request on <a href="https://github.com/Birmania/smtp-mailing-queue" rel="nofollow ugc">github</a>.

SMTP Mailing Queue

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

Mail Debug vs SMTP Mailing Queue