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MailerLite Classic

Estimated reading: 2 minutes Updated August 1, 2026

MailerLite is a popular email-marketing platform with over 1M users. This integration covers MailerLite Classic, for the new MailerLite (relaunched in 2022), see the separate MailerLite integration. Advanced Form Integration sends every form submission to a MailerLite group, mapping form fields to standard and custom subscriber fields.

What you’ll need

  • An active MailerLite Classic account.
  • A MailerLite API key.
  • At least one group / list configured.
  • The Advanced Form Integration plugin installed and activated.

Get your MailerLite Classic API key

  1. Log in to your MailerLite Classic account.
  2. Click your profile avatar (top right) → Integrations.
  3. Click API under MailerLite API.
  4. Copy the API key.

Connect MailerLite Classic to AFI

  1. In WordPress, go to AFI → Settings → MailerLite Classic.
  2. Paste the API Key and click Save Changes.

Create the integration

  1. Go to AFI → Add New.
  2. Configure the trigger.
  3. In Action → Platform, select MailerLite Classic.
  4. In Task, choose Add Subscriber or Update Subscriber.
  5. Pick the Group the subscriber should be added to.
  6. Map the form fields:
  • Email (required).
  • Name, Last Name, Phone, Company: common standard fields.
  • Custom fields appear in the dropdown using their field key.
  1. Optional: configure Conditional Logic.
  2. Click Save Integration.

Screenshot: AFI field-mapping screen with MailerLite Classic fields visible

Tasks supported

Add Subscriber

Adds a new subscriber to the chosen group. If the email already exists in MailerLite, the subscriber’s data is updated rather than duplicated.

Update Subscriber

Updates an existing subscriber’s fields by email match.

Conditional logic example

Goal: route premium-plan signups to a “Premium Subscribers” group, free-plan signups to a “Free Trial” group.

Create two integrations on the same form, each pointing at a different MailerLite group. Add the matching Equal To condition on the plan field for each.

Troubleshooting

Subscriber not added

Common MailerLite errors:

  • Invalid email: the value mapped to email isn’t a valid format.
  • Invalid API key: re-copy from MailerLite Classic Integrations page.
  • Subscriber unsubscribed: the email previously unsubscribed and MailerLite blocks re-add.

MailerLite Classic vs MailerLite (new)

MailerLite relaunched as a new platform in 2022 with a different API. Accounts created before that date are on Classic. Check your account dashboard URL. Classic uses app.mailerlite.com, new MailerLite uses dashboard.mailerlite.com. Use the right AFI integration for your account.

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