How to Write a Custom HTML Email

Most emails are quickest to build in the visual editor. But if you already have an email in HTML, from a designer, another platform or your own code, you can use it as is with a custom HTML email.

You can send a custom HTML email as a campaign, in an automation or as a transactional email, just like any other email.

Custom HTML emails are available on paid plans.

Create one

Go to Emails in the sidebar.
Click the arrow next to New draft and choose Custom HTML email.
Paste in your HTML, or edit the starter template.

You can't switch an email between custom HTML and the visual editor later, so pick the one you want when you create it.

Editing

Your HTML is on the left and a live preview of the email is on the right. Switch the preview between desktop and mobile to check how it looks on a phone, and use Format to tidy up your code.

Changes save automatically, and teammates can edit the same email with you at the same time.

Personalize it

Click Personalize to add a subscriber's first name or email address. For example, {{merge.first_name|there}} shows their first name, or "there" if you don't have it. Any of your custom fields work the same way. See personalizing your emails for more.

Unsubscribe link

Every email needs an unsubscribe link. Click Unsubscribe link in the toolbar to add Unsubscribe and Manage preferences links to the bottom of your email.

If your email doesn't have one, you'll see a reminder over the preview, and you won't be able to publish until you add it.

Images

Images need to be hosted on Audienceful. Click Image to upload one or pick one you've used before.

If your HTML uses images from somewhere else, a reminder over the preview offers to host them, and Audienceful copies them over for you. You can't publish until every image is hosted.

Tips for HTML that works in every inbox

Email clients are much stricter than web browsers. If you're writing the HTML yourself:

Lay the email out with tables (role="presentation") around 600px wide, rather than flexbox or grid.
Put styles inline on each element. Keep a <style> block for things inline styles can't do, like mobile media queries.
Use web-safe fonts, with a fallback after any Google Font.
Give every image alt text and a width, so the layout holds when images are blocked.
Use full https:// links.

Before you send

Anything email clients can't run, like scripts and forms, is removed when the email sends.
Custom HTML emails go through the same spam checks as every other email. See keeping your emails out of the spam folder.
Keep emails under about 100 KB. Gmail cuts off longer emails, and the size is shown in the toolbar.
Send yourself a test and check it on your phone before a big send.

Use the AI agent or MCP

Custom HTML emails work with the Audienceful AI agent and the Audienceful MCP server, so you can also create and edit them from Claude, ChatGPT and other AI assistants.

Write one: ask for it by name, like "write a custom HTML email announcing our holiday sale." If you don't mention HTML, the email is built in the visual editor.
Edit one: ask for a change, like "change the headline to 'Gifts for every coffee lover'."