Post SMTP Mailer/Email Log – Best Mail SMTP For WP WordPress 插件

Post SMTP Mailer/Email Log – Best Mail SMTP For WP WordPress 插件


WordPress Mail SMTP Plugin

Post SMTP is a next-generation WP Mail SMTP plugin that assists and improves the email deliverability process of your WordPress website.

Easy-to-use and reliable – 300,000+ customers trust Post SMTP Mailer to send their daily WordPress emails to millions of users worldwide.

Post SMTP is not another WP Mail SMTP clone like WP Bank or Easy SMTP. It helps provide authentication that makes sure your emails get delivered and don’t end up in the spam filter or worse, the undelivered email queue.

Post SMTP replaces the default WordPress SMTP library, PHPMailer, with the heavy-duty Zend_Mail – Never lose an email to PHP mail() again.

What makes Post SMTP the best WP Mail SMTP plugin?

  • Post SMTP’s intelligent setup wizard helps guide you each and every step of the way from getting started to sending test emails.
  • The connectivity test scans your SMTP server to detect firewall blocks and eliminate configuration mistakes.
  • The built-in Email log is an invaluable resource for diagnosing problems with emails.
  • OAuth 2.0 increase the security and protection of email password by discouraging the idea of storing your email password in the WordPress database where it might be found.

Even hosts that block the standard SMTP ports, like GoDaddy or Bluehost, can’t stop your email as Post SMTP can deliver via HTTPS if it can’t use SMTP.

Post SMTP Features

  • Easy-to-use, powerful Setup Wizard for perfect configuration
  • Commercial-grade Connectivity Tester to diagnose server issues
  • Log and resend all emails; see the exact cause of failed emails
  • Supports International alphabets, HTML Mail and MultiPart/Alternative
  • Supports forced recipients (cc, bcc, to) and custom email headers
  • SASL Support: Plain/Login/CRAM-MD5/XOAUTH2 authentication
  • Security Support: SMTPS and STARTTLS (SSL/TLS)
  • Copy configuration to other instances of Post
  • Supports the proprietary OAuth 2.0 implementations of Gmail, Hotmail and Yahoo
  • Fire-and-forget delivery continues even if you change your password.
  • Set up an app password in your Google account.

Slack notifications

Receive Post SMTP notifications on your Slack app. If you approve “Post SMTP Notifications” app for Slack, you will be notified on any selected workplace about your failed emails.

Post SMTP Notification Chrome Extension

Post SMTP Notification Chrome Extension – Install Post SMTP’s official Chrome Extension to receive notifications of failed emails on your WordPress website.

Technical Documentation

You can read our Post SMTP technical documentation for more details including setting up the plugin and configuring other SMTP options. Also, stay up-to-date on new plugin updates, changes, modifications, and related news by subscribing to the Post SMTP blog.

Help & Support

You can contact our support team by filling out the form on our website. You can raise a request for Post SMTP Mailer Supports using our support portal.

Support for Pro Extension – You can submit a support request for Post SMTP Mailer Pro Extension by visiting our support portal

Configuration Request – Having trouble configuring Post SMTP Mailer for your WordPress website? Users who are having trouble setting up or configuring the plugin can fill out the configuration request form and connect with our support team.

What is SMTP and why do you need it?

Simple Mail Transfer Protocol or SMTP is the protocol used for sending emails over the internet. Your email client uses SMTP to send a message to a mail server, which then uses SMTP to relay the message to the correct receiving mail server.

In essence, SMTP is a set of commands that authenticates and directs the transfer of electronic mail. When configuring your email program, you will typically need to set the SMTP server to your local ISP’s SMTP settings.

Looking for Post SMTP Pro Extensions?

Post SMTP Pro Extensions are everything you need to enhance your WordPress email deliverability experience. Check our extensions for Amazon SES, Better Email Logger and Office365.

Office365 API delivery
Office365 Pro extension allows you to connect PostSMTP with your Outlook and Microsoft 365 accounts to improve email deliverability.

Amazon SES API delivery?
Amazon SES Pro Extension combines Amazon’s mail service provider with PostSMTP’s powerful and easy-to-use SMTP mailing features.

Twilio Pro Extension
Twilio Extension allows you to add your phone number so that you can receive SMS notifications and alerts when emails are not delivered to your recipients.

Better Email Logger Extension?
Better Email Logger Pro extension allows you to design email marketing campaigns and improve email deliverability for your WordPress site.

Mail Control Pro Extension
Mail Control Pro Extension allows you to control Post SMTP’s email actions like sending email alerts to authors, webmasters, and new users.

Post SMTP Membership Plans

Post SMTP membership plans offer access to all pro extensions along with other benefits including 1-year extension updates and support, Email Reporting, Logging, and Tracking, all other SMTP Services and a 30-day money-back guarantee.

API (HTTPS) Email Support for different SMTPs

  • Gmail API for sending Gmail and Google Apps email (requires a Google account)
    Often bloggers and small business owners don’t want to use third-party SMTP services. Well you can use your Gmail or G Suite account for SMTP emails.

  • Mandrill API for sending any email (requires a Mandrill account)
    Mandrill is an email infrastructure service offered as an add-on for MailChimp that you can use to send personalized, one-to-one e-commerce emails, or automated transactional emails.

  • Mailgun API for sending any email (requires a Mailgun account)
    Mailgun SMTP is a popular SMTP service provider that allows you to send large quantities of emails. They allow you to send your first 10,000 emails for free every month.

  • SendGrid API for sending any email (requires a SendGrid account and PHP 5.3)
    SendGrid has a free SMTP plan that you can use to send up to 100 emails per day. With our native SendGrid SMTP integration, you can easily and securely set up SendGrid SMTP on your WordPress site.

  • Sendinblue API for sending any email (requires a Sendinblue account and PHP 5.3)
    SendinBlue is an effective and great email software for Small to Medium businesses. You can build customer relationships with an all-in-one digital marketing toolbox. Their free plan allows you to send up to 300 emails per day.

Compatibility & Support

  • Contact Form 7
  • Woocommerce
  • New User Approve
  • Password Protected
  • Elementor Forms
  • Gravity Forms
  • Login Designer
  • Visual Forms Builder
  • Mailster Newsletter plugin
  • SendPress Newsletters
  • WP HTML Mail
  • Email Templates
  • .. and every other plugin that uses the WordPress API wp_mail to send mail!


  • WordPress 5.6 and PHP 5.6 with SPL and iconv
  • Memory: 750KiB per process at idle
  • Reliable mail delivery with custom email domains requires an SPF record
  • Reliable SMTP delivery requires credentials with an email service provider

Grant OAuth permission error messages

Please note that the Client ID and Client Secret fields are NOT for your username and password. They are for OAuth Credentials only.

Error authenticating with this Client ID. [Error executing wp_remote_post: The user has blocked requests via HTTP.]

Your WordPress site is configured with WP_HTTP_BLOCK_EXTERNAL to prevent outbound connections. Add a whitelist rule to wp-config.php:

define(‘WP_ACCESSIBLE_HOSTS’, ‘,,’);

Error authenticating with this Client ID. [Error executing wp_remote_post: Failed to connect to xxxx]

There is a firewall on port 443 between you and the OAuth2 server. Open up the port for outbound connections.

Error: redirect_uri_mismatch

  • You did not enter the Redirect URI correctly.
  • You used an IP address instead of a domain name (not allowed)

SMTP Error Messages

Communication Error 334 make sure the Envelope From Email is the same account used to create the Client ID.

  • This is almost always caused by being logged in to Google/Microsoft/Yahoo with a different user than the one Post is configured to send mail with. Logout and try again with the correct user
  • Login to Webmail and see if there is an “Unusual Activity” warning waiting for your attention

Could not open socket

  • Your host may have installed a firewall between you and the server. Ask them to open the ports.
  • Your may have tried to (incorrectly) use SSL over port 587. Check your encryption and port settings.

Operation Timed out

  • Your host may have poor connectivity to the mail server. Try doubling the Read Timeout.
  • Your host may have installed a firewall (DROP packets) between you and the server. Ask them to open the ports.
  • Your may have tried to (incorrectly) use TLS over port 465. Check your encryption and port settings.

Connection refused

Your host has likely installed a firewall (REJECT packets) between you and the server. Ask them to open the ports.

503 Bad sequence of commands

You configured TLS security when you should have selected no security.

XOAUTH2 authentication mechanism not supported

You may be on a Virtual Private Server that is playing havoc with your communications. Jump ship.

Mail ends up in the Spam folder

To avoid being flagged as spam, you need to prove your email isn’t forged. On a custom domain, its up to YOU to set that up:

  • Ensure you are using the correct SMTP server with authentication – the correct SMTP server is the one defined by your email service’s SPF record
  • If you use a custom domain name for email, add an SPF record to your DNS zone file. The SPF is specific to your email provider.
  • 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).



2024-07-11 10:50:13