Have you set up forms on your WordPress site, only to find that their email notifications aren't reaching recipients' inboxes? It's common to see email delivery issues in WordPress, but you can easily fix them using WP Mail SMTP for reliable, authenticated email delivery.

In this tutorial, we'll show you how to use WP Mail SMTP to fix email delivery issues on your WordPress site.

  • Why Aren't Emails Getting Delivered?
  • Fixing Email Delivery Issues With WP Mail SMTP
  • Setting Up the Other SMTP Mailer in WP Mail SMTP
  • SMTP Settings for Popular Providers
  • Frequently Asked Questions

Why Aren't Emails Getting Delivered?

There are two main reasons why WordPress emails don't deliver successfully: server configuration and spam filtering.

WordPress and WordPress plugins send email using the PHP mail() function by default. This is a simple way of sending email, but many WordPress hosting servers are not configured to use this mail() function.

In addition, email providers check each incoming email to determine if they should allow the email to deliver, send it to spam, or block it entirely. One way email providers do this is by checking if the email originates from the same location it claims to be sent from.

For example, if your email server is gmail.com but your email claims to be sent from your website's domain, email providers may block your form notification before it even reaches users' spam folders.

Fixing Email Delivery Issues With WP Mail SMTP

SMTP (Simple Mail Transfer Protocol) fixes email delivery issues by changing the way your site sends emails and by properly authenticating them. SMTP is the industry standard for ensuring email deliverability, and WP Mail SMTP is the most flexible way to connect to many different SMTP services (called "mailers").

Below is a list of all of the mailers you can use to set up SMTP on your site through WP Mail SMTP, along with links to tutorials on each:

  • SendLayer (recommended): A fast, secure, and reliable email delivery and authentication service that allows you to send mail from an address on your own domain through our secure API or SMTP.
  • SMTP.com (recommended): A well-established market leader in email delivery services.
  • Sendinblue (recommended): This platform offers email marketing features as well as improved email delivery. It has a limited free plan available that is ideal for small businesses.
  • Amazon SES: A secure and effective solution for improving email delivery. However, it does have a more technical setup process, so we only recommend this option for advanced users.
  • Google Workspace / Gmail: Using Google's secure API, you can improve email delivery for emails sent from a Gmail address or Google email alias.
  • Mailgun: This mailer offers competitive pricing and allows you to authenticate emails using any email address.
  • Microsoft 365 / Outlook.com: If you're already using Microsoft 365 for your business, you can easily connect it to your site via WP Mail SMTP for improved email delivery.
  • Postmark: Specializing in email delivery, Postmark includes features such as segmentation and message streams to keep all the emails sent from your site organized.
  • SendGrid: Another popular and affordable option for small businesses.
  • SparkPost: For large-scale businesses, SparkPost is a trusted platform for authenticating emails and improving delivery rates.
  • Zoho Mail: A highly secure email service. It also has several CRM features you can use for your business.
  • Other SMTP: This is the least secure mailer option offered by WP Mail SMTP, but it enables you to set up a custom SMTP configuration.

Setting Up the Other SMTP Mailer in WP Mail SMTP

SMTP must be able to connect to your email provider, which is why it requires additional setup through a plugin like WP Mail SMTP.

Unlike our other options, which use APIs to store setup information with your mailer, the Other SMTP option in WP Mail SMTP stores this setup information directly on your site.

Below, we'll go into more detail on each of the settings required to set up the Other SMTP mailer in WP Mail SMTP.

SMTP Host

This is the address to the host's SMTP server.

SMTP Port

The most common ports are 587 and 465. However, hosts can and do change these. It's not uncommon for web hosts to block these ports, so before you begin it's always good to verify with your web host that the required port is open. If it's closed, most of the time your hosting provider can open it for you.

Encryption

SSL and TLS are the most widely used encryptions. If your email provider offers both, we recommend TLS. It is worth noting that usually TLS encryption is used with port 587, while SSL is used with port 465.

Authentication

Modern email providers require authentication. Disabling it may be needed for local development or other edge case scenarios. However, most providers need this setting turned on.

SMTP Username

Your username is typically your email address for the email provider (e.g., [email protected] or [email protected]). Some providers such as AOL require the non-email format (e.g., if your email is [email protected] your username is sullie_eloso).

SMTP Password

This is your email account password.

Other SMTP settings in WP Mail SMTP

SMTP Settings for Popular Providers

When filling out the fields mentioned above, the settings you'll need depend on your email provider.

Here are the SMTP settings you'll need for the most popular email providers.

Gmail / Google Workspace SMTP Settings

Host: smtp.gmail.com
Port: 587 (or 465 using SSL encryption)
Username: Your Gmail account email address ([email protected])
Password: You will need to generate an app password in Google
Encryption: TLS

Outlook.com SMTP Settings

Host: smtp-mail.outlook.com
Port: 587
Username: Your Outlook.com account email (e.g. [email protected])
Password: You'll need to generate an app password
Encryption: TLS

Office 365 SMTP Settings

Host: smtp.office365.com
Port: 587
Username: Your Office 365 account email
Password: You'll need to generate an app password
Encryption: TLS

Note: We recommend using the built-in Microsoft 365 / Outlook option instead of connecting Outlook through the Other SMTP mailer.

Hotmail SMTP Settings

Host: smtp.live.com
Port: 587
Username: Your Hotmail account email (e.g. [email protected])
Password: You'll need to generate an app password
Encryption: TLS

Yahoo Mail SMTP Settings

Host: smtp.mail.yahoo.com
Port: 465
Username: Your Yahoo Mail account email (e.g. [email protected])
Password: You'll need to to generate an app password in Yahoo
Encryption: SSL

AOL SMTP Settings

Host: smtp.aol.com
Port: 587
Username: Your AOL screen name (e.g. sullie)
Password: You'll need to generate an app password
Encryption: TLS

Zoho Mail SMTP Settings

Zoho offers two types of email addresses: free accounts (i.e., [email protected]) and domain-based accounts (i.e., [email protected]). Each type of email requires different SMTP settings. We've shared both sets below.

Note: We recommend using the built-in Zoho Mail option instead of connecting Zoho through the Other SMTP mailer.

Emails @zoho.com

Host: smtp.zoho.com
Port: 587 (or 465 using SSL encryption)
Username: Your Zoho Mail account email (e.g. [email protected])
Password: You'll need to to generate an app password in Zoho
Encryption: TLS

Emails @yourdomain.com

Host: smtppro.zoho.com
Port: 587 (or 465 using SSL encryption)
Username: Your domain-based email (e.g. [email protected])
Password: You'll need to to generate an app password in Zoho
Encryption:TLS

Frequently Asked Questions and Common Issues

Below, we've answered some of the most common questions about improving email notification delivery for your forms with WP Mail SMTP.

My SMTP test email delivers successfully, so why aren't my form notification emails delivering?

If your test email is successful, this means that SMTP is working properly. Instead, you'll need to check the form's notification settings by opening the form builder and going to Settings » Notifications.

From here, you can check all the settings. However, specifically note the From Email, as this must meet the requirements set by your WP Mail SMTP mailer.

My site's hosting provider is GoDaddy and I can't get SMTP to work. What can I do?

In many cases, GoDaddy will, by default, block the ports SMTP requires. To address this, you'll need to reach out to GoDaddy's support to ask them to open up the port you need for your site.

I'm seeing an error message. How do I fix it?

Here are solutions for the most common SMTP error messages.

Error: Could Not Open Socket

This usually happens when your web host is blocking the ports required to connect. A lot of times this is due to a firewall that is running. Contact your host and ask them to open the port you need.

Also, double-check your port and encryption settings, as accidentally using SSL over port 587 can trigger this error.

Error: smtp connect() failed

This error means the connection to the SMTP host failed. You'll typically see this error when your SMTP settings are incorrect or the SMTP host is denying or blocking the connection for security purposes.

Some hosting providers, such as GoDaddy, may specifically be blocking the port needed for SMTP.

Be sure to double-check all of your settings, including your email and password. If the error persists, the best next step is to contact your site's hosting provider to ask them to check for any server issues.

Error: Connection Refused

A firewall may be preventing the connection. Contact your web host and ask them to open the required port.

Error: Mod_Security

"Not Acceptable! An appropriate representation of the requested resource could not be found on this server. This error was generated by Mod_Security."

This error most commonly occurs when the server is blocking requests needed to run SMTP. To fix this, you'll need to contact your site's hosting provider and ask them to disable specific rules within Mod_Security, which they can determine using server logs.

Error: 535 Incorrect authentication data

"SMTP ERROR: Password command failed: 535 Incorrect authentication data"

This error generally results from overly strict server permissions, which your hosting provider should be able to help you resolve. For WHM / cPanel server management, you can specifically ask your site's hosting provider to switch the "Restrict outgoing SMTP to root, exim, and mailman" setting from "On" to "Off."

That's it! Now you know everything you need to know to start improving email delivery for your form notifications using WP Mail SMTP.

Next, would you like to learn how to set up conditional email notifications to send different messages depending on how users fill out your forms? Check out our full tutorial on conditional notifications.