Errors in a custom code email

Possible errors and warnings in a custom HTML code email and how to resolve them

When creating an email in our Custom Code editor, we automatically check your HTML for potential issues that could prevent your email from sending or from displaying the way you intend. While some of these issues are minor and you can still send your email without resolving them, others will prevent you from sending until they’re fixed.

• Errors that prevent you from sending
• Errors that don’t prevent you from sending
• List of supported HTML tags

Errors that prevent you from sending

Certain errors found in your HTML require you to fix them before you can send your email. You’ll have the option for us to fix them for you, but you should preview your email before sending to make sure everything displays as intended. These issues will appear at the top of the email with a red X icon .

Open pixel missing

In order to track email opens, we use a transparent, single-pixel image embedded in your emails that tells when a contact has or has not opened a specific email. If the Tracking Image tag has been deleted from the code, you’ll receive an error and will need to reinsert it by clicking Insert > Tracking Image.

Multiple open pixels found

If more than one Tracking Image tag is found in your HTML, you’ll also receive an error and will need to delete any extra instances of [[trackingImage]] until you only have one in your code.

Unsupported HTML tags or parameters

If your HTML includes a tag or parameter that is not valid (for example, if you have a typo in the tag name) or a tag that we don't allow either for security reasons or because most email clients don't support it, you’ll receive an error that it’s not a supported tag. You’ll need to either fix the tag or delete it from the code before you can send the email. If you’re trying to include personalized contact details in your email, use this list of personalization tags.

Email too large

The maximum email size is 400 KB. If your email is larger than that, you’ll need to remove some content before you can send the email. Keeping your email short also helps to increase engagement with your contacts.

Illegal characters

• [#
• ${
• <@

If any of these are found in your HTML, you’ll need to remove them from the code.

Errors that don’t prevent you from sending

Some issues that are found aren’t a huge deal and you can send your email without fixing them, but we recommend you review them before continuing. These issues will appear at the top of the email with a blue information icon .

Unsupported HTML attributes

If you have an invalid attribute in your HTML (for example, if there’s a typo in the attribute name) or you have proprietary attributes from programs like DreamWeaver, you’ll receive a warning that it’s not a supported attribute. You can choose to fix it or delete it from the code, otherwise it’ll be stripped out of the email when it’s sent. We recommend sending a test of your email to make sure it displays properly.

Bad HTML formatting 

Some issues with your code will also result in a warning, such as missing closing brackets or quotes. To ensure your email displays the way you intend, all tags should be escaped (< >) and paired with an open or close tag. If any of these issues are found, they’ll be stripped out of the email when it’s sent.

List of supported HTML tags

Questions?