Inline image attachments with wp_mail()

[jesin]

To insert inline images in an email the phpmailer_init action hook has to be used like this.

add_action( 'phpmailer_init', 'embed_images' );

function embed_images( &$phpmailer ) {
    $phpmailer->AddEmbeddedImage( '/path/to/image1.png', 'image1.png' );
    $phpmailer->AddEmbeddedImage( '/path/to/image2.png', 'image2.png' );
    $phpmailer->AddEmbeddedImage( '/path/to/image3.png', 'image3.png' );
}

Why not implement this in wp_mail() itself?

[jesin]

Add inline images using wp_mail()

[jesin]

Update 28059.diff

[swissspidy]

According to the docs, $phpmailer->addEmbeddedImage is only useful for HTML messages. What happens when you use that in a text email?

[jesin]

Replying to swissspidy:

According to the docs, $phpmailer->addEmbeddedImage is only useful for HTML messages. What happens when you use that in a text email?

In a text message the email client shows the image as an attachment. I tested this on Gmail and Outlook.com.

[chris@…]

I'm not sure if this is needed at the wp_mail level or not (although I needed to do the workaround today) but if this gets refreshed I wouldn't blindly assume that basename( $embed ) is valid for the $cid parameter.

Most people probably have image-1.png and image-2.png but it could be http://example.com/cats/logo.png and http://example.com/dogs/logo.png and basename() would turn them both into logo.png.

After 10 years of this patch I still find this relevant, so I'm refreshing it

Following the advice of @chrisvendiadvertisingcom, I've added an improved way to have unique cids with md5

In the next message, I will be providing some testing info

Trac ticket: https://core.trac.wordpress.org/ticket/28059

[SirLouen]

Testing Instructions

1. First, you need to set up a working Mail environment:

• You might use some env like Local WP, Laravel Herd, FlyEnv, or the liking, all come with Mail testing system
• Or if you are using wordpress-develop you might try to configure my ​PR 8555 which adds Mailhog support

2. Secondly, you need to install some WP plugin (or add some code), to connect to the email delivery server. You might use some plugins like WP Mail SMTP and configure with the hostname and port of your Mail testing service.

3. Once you have the mailing system completely setup, it's time to use my testing plugin: ​https://raw.githubusercontent.com/SirLouen/wp-mail-embed-showcase/refs/tags/1.0.0/wp-mail-embed-showcase.php

• You can check the code and adapt it to your needs, in order to add whatever extra tests you would like to do.
• By default, it adds a menu called Mail Embed Showcase, which will send an email with two default embeds: A PNG and an SVG using the filter hook wp_mail_embed_args to specify the SVG file type image/svg+xml (not defaulted by PHPMailer).

4. Finally, if everything is OK, you will receive an email with the two embedded images showing.

The unit tests are going failed that needs to fixed.

[yashjawale]

Test Report

Description

This report validates whether the indicated patch works as expected.

Patch tested: ​https://github.com/WordPress/wordpress-develop/pull/9038.diff

Environment

• WordPress: 6.8.1
• PHP: 8.2.27
• Server: nginx/1.26.1
• Database: mysqli (Server: 8.0.35 / Client: mysqlnd 8.2.27)
• Browser: Chrome 138.0.0.0
• OS: macOS
• Theme: Twenty Twenty-Five 1.2
• MU Plugins: None activated
• Plugins:
  • Test Reports 1.2.0
  • WP Mail Embed Showcase 1.0.0 [SirLouen's testing plugin from comment:7]
  • WP Mail SMTP 4.5.0

Actual Results

1. ✅ Able to embed the following mimetypes:

• image/svg+xml
• image/png
• image/jpeg
• image/gif
• video/mp4
• video/quicktime
• audio/mpeg

Supplemental Artifacts

Before patch:

After patch:

[iamadisingh]

Test Report

Description

This report validates whether the indicated patch works as expected.

Patch tested: ​https://github.com/WordPress/wordpress-develop/pull/9038

Environment

• WordPress: 6.8.1
• PHP: 8.2.27
• Server: nginx/1.26.1
• Database: mysqli (Server: 8.0.35 / Client: mysqlnd 8.2.27)
• Browser: Chrome 138.0.0.0
• OS: macOS
• Theme: Twenty Twenty-Five 1.2
• MU Plugins: None activated
• Plugins:
  • Test Reports 1.2.0
  • WP Mail Embed Showcase 1.0.0
  • WP Mail SMTP 4.5.0

Actual Results

1. ✅ Issue resolved with patch.

Additional Notes

• Activated the wp-mail-embed-showcase.php plugin mentioned by @SirLouen ​https://raw.githubusercontent.com/SirLouen/wp-mail-embed-showcase/refs/tags/1.0.0/wp-mail-embed-showcase.php
• Modified the plugin code to check for image/gif
• Able to embed following mime types:
  • image/gif
  • image/png
  • image/svg+xml

Supplemental Artifacts

Before Patch Screenshot: ​https://ibb.co/pBfx4NBr
After Patch Screenshot: ​https://ibb.co/Z6w1ZYyW