Postman is a next-generation SMTP Mailer, software that assists in the delivery of email generated by your WordPress site.

Postman SMTP Mailer/Email Log

<p>Postman is a next-generation <a href="https://wordpress.org/plugins/search.php?q=smtp">SMTP Mailer</a>, software that assists in the delivery of email generated by your WordPress site. Postman is the first and only plugin to support the <a href="http://googleonlinesecurity.blogspot.ca/2014/04/new-security-measures-will-affect-older.html" rel="nofollow">latest security standards</a>. With OAuth 2.0, there is <strong>no need</strong> to <a href="http://blog.codinghorror.com/youre-probably-storing-passwords-incorrectly/" rel="nofollow">store your email passsword</a> in the WordPress database where it might be found.</p>
<blockquote>
<p>Postman is one year old! SparkPost API Integration is coming soon as Mandrill is no longer offering a free service.</p>
</blockquote>
<p>The <strong>Connectivity Test</strong> and intelligent <strong>Setup Wizard</strong> scan your SMTP server to detect firewall blocks and eliminate configuration mistakes. The built-in <strong>Email Log</strong> is an invaluable resource for <a href="https://wordpress.org/support/topic/ugly-e-mails-no-html-and-no-special-characters?replies=15" rel="nofollow">diagnosing problems</a> with emails. Even hosts that block the standard SMTP ports, like GoDaddy or Bluehost, can&#8217;t stop your email as <strong>Postman can deliver via HTTPS</strong> if it can&#8217;t use SMTP.</p>
<p>Postman is <em>not</em> another WP Mail SMTP clone like WP Bank or Easy SMTP. It replaces the default WordPress SMTP library, PHPMailer, with the heavy-duty Zend_Mail. Never <a href="http://www.jvfconsulting.com/blog/php-mail-function-vs-smtp-guaranteed-delivery/" rel="nofollow">lose an email to PHP mail()</a> again.</p>
<h4>Standard Features</h4>
<ul>
<li>Easy-to-use, powerful Setup Wizard for perfect configuration</li>
<li>Commercial-grade Connectivity Tester to diagnose server issues</li>
<li>Log and resend all emails; see the exact cause of failed emails</li>
<li>Supports <a href="https://tools.ietf.org/html/rfc6530" rel="nofollow">International alphabets</a>, <a href="https://en.wikipedia.org/wiki/HTML_email" rel="nofollow">HTML Mail</a> and <a href="https://en.wikipedia.org/wiki/MIME#Alternative" rel="nofollow">MultiPart/Alternative</a></li>
<li>Supports forced recipients (cc, bcc, to) and custom email headers</li>
<li><a href="https://en.wikipedia.org/wiki/Simple_Authentication_and_Security_Layer" rel="nofollow">SASL</a> Support: Plain/Login/CRAM-MD5/<a href="https://en.wikipedia.org/wiki/OAuth#OAuth_2.0" rel="nofollow">XOAUTH2</a> authentication</li>
<li>Security Support: <a href="https://en.wikipedia.org/wiki/SMTPS" rel="nofollow">SMTPS</a> and <a href="https://en.wikipedia.org/wiki/STARTTLS" rel="nofollow">STARTTLS</a> (<a href="https://en.wikipedia.org/wiki/Transport_Layer_Security" rel="nofollow">SSL/TLS</a>)</li>
<li>Copy configuration to other instances of Postman</li>
</ul>
<h4>OAuth 2.0 Features</h4>
<ul>
<li>Supports the proprietary OAuth 2.0 implementations of Gmail, Hotmail and Yahoo</li>
<li>Fire-and-forget delivery continues even if your password changes</li>
<li>Gmail: By combining OAuth2 and the Gmail API, Postman can deliver where other plugins can not</li>
</ul>
<h4>WebService (HTTPS) Email Features</h4>
<ul>
<li>Gmail API for sending Gmail and Google Apps email (requires a <a href="https://accounts.google.com/signup" rel="nofollow">Google</a> account)</li>
<li>Mandrill API for sending any email (requires a <a href="http://www.mandrillapp.com" rel="nofollow">Mandrill</a> account)</li>
<li>COMING SOON: Sparkpost API for sending any email (requires a <a href="https://www.sparkpost.com" rel="nofollow">Sparkpost</a> account)</li>
<li>SendGrid API for sending any email (requires a <a href="https://sendgrid.com" rel="nofollow">SendGrid</a> account and PHP 5.3)</li>
</ul>
<blockquote>
<p>Postman needs <a href="https://translate.wordpress.org/projects/wp-plugins/postman-smtp/stable" rel="nofollow">translators</a>! If you are a non-English speaker, please get involved!</p>
</blockquote>
<h4>Compatibile With..</h4>
<ul>
<li><a href="https://wordpress.org/plugins/woocommerce/">Woocommerce</a></li>
<li><a href="https://wordpress.org/plugins/contact-form-7/">Contact Form 7</a></li>
<li><a href="http://www.gravityforms.com" rel="nofollow">Gravity Forms</a></li>
<li><a href="https://wordpress.org/plugins/si-contact-form/">Fast Secure Contact Form</a></li>
<li><a href="https://wordpress.org/plugins/visual-form-builder/">Visual Forms Builder</a></li>
<li><a href="https://wordpress.org/plugins/contact-form-builder/">Contact Form Builder</a></li>
<li><a href="https://wordpress.org/plugins/planso-forms/">PlanSo Forms</a></li>
<li><a href="http://revaxarts-themes.com/?t=mymail" rel="nofollow">MyMail Newsletter</a> by revaxarts</li>
<li><a href="https://wordpress.org/plugins/sendpress/">SendPress Newsletters</a></li>
<li><a href="https://wordpress.org/plugins/wp-html-mail/">WP HTML Mail</a></li>
<li><a href="https://wordpress.org/plugins/email-templates/">Email Templates</a></li>
<li><a href="https://wordpress.org/plugins/leads/">WordPress Leads</a></li>
<li>.. and every other plugin that uses the WordPress API <a href="https://codex.wordpress.org/Function_Reference/wp_mail" rel="nofollow">wp_mail</a> to send mail!</li>
</ul>
<h4>Requirements</h4>
<ul>
<li>WordPress 3.9 and PHP 5.2 with SPL and iconv</li>
<li>Memory: 750KiB per process at idle</li>
<li>Reliable mail delivery with custom email domains requires an SPF record</li>
<li>Reliable SMTP delivery requires credentials with an email service provider</li>
<li>OAuth 2.0 features require a Gmail, Hotmail or Yahoo mail OAuth 2.0 credentials</li>
</ul>
<h3>Grant OAuth permission error messages</h3>
<p>Please note that the Client ID and Client Secret fields are NOT for your username and password. They are for OAuth Credentials only.</p>
<h4>Error authenticating with this Client ID. [Error executing wp_remote_post: The user has blocked requests via HTTP.]</h4>
<p>Your WordPress site is configured with WP_HTTP_BLOCK_EXTERNAL to prevent outbound connections. Add a whitelist rule to wp-config.php:</p>
<blockquote>
<p>define(&#8216;WP_ACCESSIBLE_HOSTS&#8217;, &#8216;www.googleapis.com, login.live.com, api.login.yahoo.com&#8217;);</p>
</blockquote>
<h4>Error authenticating with this Client ID. [Error executing wp_remote_post: Failed to connect to xxxx]</h4>
<p>There is a firewall on port 443 between you and the OAuth2 server. Open up the port for outbound connections.</p>
<h4>Error: redirect_uri_mismatch</h4>
<ul>
<li>You did not enter the Redirect URI correctly, watch the <a href="https://vimeo.com/128589255" rel="nofollow">instructional video</a></li>
<li>You used an IP address instead of a domain name (not allowed)</li>
</ul>
<h4>Error: invalid_client &#8230; no support email</h4>
<p>You&#8217;ve <a href="https://wordpress.org/support/topic/status-postman-is-not-sending-mail-1?replies=7" rel="nofollow">forgotten to choose an email address in the consent screen</a>.</p>
<h3>SMTP Error Messages</h3>
<h4>Communication Error [334] – make sure the Envelope From Email is the same account used to create the Client ID.</h4>
<ul>
<li>This is almost always caused by being logged in to Google/Microsoft/Yahoo with a different user than the one Postman is configured to send mail with. Logout and try again with the correct user</li>
<li>Login to <a href="http://www.gmail.com" rel="nofollow">Webmail</a> and see if there is an &#8220;Unusual Activity&#8221; warning waiting for your attention</li>
</ul>
<h4>Could not open socket</h4>
<ul>
<li>Your host may have installed a firewall between you and the server. Ask them to open the ports.</li>
<li>Your may have tried to (incorrectly) use SSL over port 587. Check your encryption and port settings.</li>
</ul>
<h4>Operation Timed out</h4>
<ul>
<li>Your host may have poor connectivity to the mail server. Try doubling the Read Timeout.</li>
<li>Your host may have installed a firewall (DROP packets) between you and the server. Ask them to open the ports.</li>
<li>Your may have tried to (incorrectly) use TLS over port 465. Check your encryption and port settings.</li>
</ul>
<h4>Connection refused</h4>
<p>Your host has likely installed a firewall (REJECT packets) between you and the server. Ask them to open the ports.</p>
<h4>503 Bad sequence of commands</h4>
<p>You configured TLS security when you should have selected no security.</p>
<h4>XOAUTH2 authentication mechanism not supported</h4>
<p>You may be on a Virtual Private Server that is <a href="https://wordpress.org/support/topic/oh-bother-xoauth2-authentication-mechanism-not-supported?replies=9" rel="nofollow">playing havoc with your communications</a>. Jump ship.</p>
<h3>Mail ends up in the Spam folder</h3>
<p>To avoid being flagged as spam, you need to prove your email isn&#8217;t forged. On a custom domain, its up to YOU to set that up:</p>
<ul>
<li>Ensure you are using the correct SMTP server with authentication &#8211; the correct SMTP server is the one defined by your email service&#8217;s SPF record</li>
<li>If you use a custom domain name for email, add an <a href="http://www.openspf.org/Introduction" rel="nofollow">SPF record</a> to your DNS zone file. The SPF is specific to your email provider, for example <a href="https://support.google.com/a/answer/33786" rel="nofollow">Google</a></li>
<li>If you use a custom domain name for email, add a DKIM record to your DNS zone file and upload your Domain Key (a digital signature) to, for example <a href="//support.google.com/a/answer/174124?hl=en)" rel="nofollow">Google</a></li>
</ul>


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