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Importing into Your ESP

Every email service provider (ESP) has a slightly different interface, but the process for importing custom HTML is generally the same.

The standard workflow

Section titled “The standard workflow”

Most ESPs offer an option to create a campaign using your own HTML. Look for options labelled “Import HTML,” “Custom Code,” “Code your own,” or “HTML Editor.”

  1. Open your exported .html file in a text editor
  2. Select all the code and copy it to your clipboard
  3. In your ESP, create a new email campaign
  4. Find the option to paste or import custom HTML (this is usually an alternative to the ESP’s drag-and-drop editor)
  5. Paste your HTML into the code editor
  6. Preview your email and proceed with the ESP’s normal sending flow

If you cannot find the import option, search your ESP’s help center for “import HTML” or “custom code.”

Common ESPs

Section titled “Common ESPs”

These platforms all support custom HTML import:

  • Mailchimp
  • Klaviyo
  • Campaign Monitor
  • Brevo (formerly Sendinblue)
  • HubSpot
  • Salesforce Marketing Cloud
  • ActiveCampaign
  • Constant Contact
  • Drip
  • Customer.io

Check your ESP’s documentation for specific instructions. Interface locations change frequently.

Why emails might look different in your ESP

Section titled “Why emails might look different in your ESP”

Code modification. Some ESPs automatically “fix” or modify your HTML. Look for settings that ensure the ESP uses your HTML exactly as pasted.

Double CSS inlining. Some ESPs try to inline CSS again, which can cause conflicts. If possible, turn off automatic CSS inlining in your ESP settings.

Link tracking. Most ESPs wrap your links with tracking URLs for analytics. This is usually fine, but send a test email to verify all links work as expected.

Troubleshooting

Section titled “Troubleshooting”

Check the DOCTYPE. Ensure your ESP has not stripped the <!DOCTYPE html> declaration from the top of your file. Missing doctypes can cause rendering issues.

Verify image paths. If images appear broken, check if the ESP has rewritten the src paths. Image URLs should be absolute (e.g., https://your-domain.com/image.jpg) and publicly accessible.

Send a test. The only way to be certain how an email will look is to send a real test through the ESP. Previews within the ESP are not always accurate. Send tests to Gmail, Outlook, and Apple Mail at minimum.