Enterprise Business Use Cases
Automated Lead Magnet Delivery
When a user fills out a form to download an eBook, Flex Forms instantly assigns them to a specific MailerLite Group (e.g., “Ebook Downloaders”). This Group assignment acts as the trigger for a MailerLite automation to instantly deliver the PDF via email.
Hyper-Personalized Newsletters
Seamlessly collect custom demographic data (like location or industry) via a Flex Form and map it directly to Custom Fields in MailerLite. This allows you to send highly personalized, hyper-targeted weekly broadcast emails.
Ultra-Detailed, Step-by-Step Setup Guide
Connecting Flex Forms to MailerLite requires generating a specific API Token. Follow these exact instructions to ensure the integration is properly authenticated.1
Step 1: Log into MailerLite
Open your web browser and navigate to your MailerLite login portal. Enter your credentials to access the main dashboard.
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Step 2: Access the Integrations Menu
Once logged in, look at the left-hand sidebar navigation menu. Scroll down the list until you find the section labeled Integrations. Click exactly on this link.
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Step 3: Locate the MailerLite API Section
You are now on the Integrations overview page, which lists dozens of third-party apps. Look specifically for the box labeled MailerLite API.
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Step 4: Enter the API Management Interface
Click the prominent button labeled Use (or Manage) located inside the “MailerLite API” box. This will take you to the secure token generation center.
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Step 5: Initiate Token Generation
Look for the button labeled Generate new token. Click it. A configuration modal will appear.
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Step 6: Name the Token
In the “Token name” field, type exactly:
Flex Forms Website Integration. Giving it a descriptive name ensures you will not accidentally delete it during future security reviews. Click the Create token button.7
Step 7: Copy the API Token
MailerLite will instantly generate a very long string of alphanumeric characters.Click the Copy button (or highlight the string and press
CRITICAL WARNING: You must copy this token immediately. For security reasons, MailerLite will never display this token to you again. If you lose it or close the window too early, you must revoke it and generate a new one.
Ctrl+C / Cmd+C). After verifying it is on your clipboard, click “Download” just to be safe, then click the button to close the modal.8
Step 8: Create a Connection (recommended)
Switch to Flex Forms → Integrations → Connections. Create a MailerLite connection, paste the API token, and connect. Catalog → MailerLite remains available for a single shared account.
Masterclass: Mapping Data Payloads
Establishing the connection allows data to flow, but you must instruct Flex Forms on exactly how to organize that data once it arrives in MailerLite. In MailerLite, you organize and segment contacts using Groups (formerly called Lists). You MUST provide the specificGroup ID in the Flex Forms integration settings for the target form to ensure the subscriber is categorized correctly.
Finding the Group ID
In MailerLite, you organize and segment contacts using Groups (formerly called Lists).Built-in API Sync: You do NOT need to manually hunt for Group IDs. As long as your Global API Key is valid, Flex Forms automatically queries MailerLite and provides a live dropdown of all your available Groups directly on the form hub Integrations tab.
- Standard Field Mapping
- Exact Mapping Example
The primary Email address is synced automatically by Flex Forms. You must map any additional fields to MailerLite’s standard fields (like
name, last_name, company, city, phone).The format is always: mailerlite_field=flex_forms_block_nameHow Custom Fields Work in MailerLite
If you want to send data that MailerLite doesn’t support by default (e.g.,Dietary_Preference), you must manually create that Custom Field in MailerLite first (Subscribers > Custom Fields).
When mapping, you MUST use the exact Internal Key generated by MailerLite, NOT the human-readable name.
The Formatting Trap: If you name your field “Dietary Preference” in MailerLite, its internal key is actually
dietary_preference. If you map Dietary Preference=dropdown (with spaces and capital letters), the MailerLite API will instantly reject the entire payload as a malformed request.Troubleshooting & Enterprise FAQs
Updating Existing Subscribers
Updating Existing Subscribers
The Problem: What happens if a user who is already subscribed to my MailerLite account fills out the Flex Form again to download a new eBook?The Solution: Flex Forms intelligently handles this without throwing duplicate errors. It uses the email address as the primary key. If the subscriber already exists, Flex Forms will gracefully update their custom fields with any new information provided in the form, and it will safely append the new Group assignment to their existing profile.
Configuration Reference
The following advanced settings are available in the Flex Forms UI for this integration. Use this reference to understand exactly how each field impacts the API payload.Global Settings
Located in Integrations in the Flex Forms left rail.password
required
MailerLite API Token
Your secure API token for MailerLite’s new v2 API. Generate this inside your MailerLite account by navigating to Integrations → API → Generate new token.
Form-Level Settings
Located on the form hub Integrations tab for a specific form.Subscriber Placement
remote_select
MailerLite group
Optional. Select the exact MailerLite Subscriber Group you want these leads added to. Flex Forms queries the API in real-time to load your actual groups into this dropdown.
text
Tag IDs
Unlike ActiveCampaign which accepts text tags, MailerLite strictly requires numeric Tag IDs (e.g.,
123456789). You can provide a comma-separated list of IDs to attach to the subscriber.remote_select
Available tags (reference)
A read-only helper dropdown. Select a tag to view its numeric ID, then copy/paste it into the
tag_ids field above.Field Mapping
select
required
Email field
The primary email block from your form. MailerLite requires this to identify the subscriber.
select
Name field
select
Last name field
textarea
Custom fields
The routing map for injecting form answers into MailerLite subscriber properties.Format requires one rule per line:
mailerlite_field_key=form_block_name.
Note: MailerLite strictly types its fields. If a MailerLite field is set to ‘date’, Flex Forms will automatically attempt to coerce your form answer into a Y-m-d format.Pro-tip: Prefix any key with a + (e.g., +company_name=company_input), and if that field doesn’t exist in MailerLite, Flex Forms will immediately call the /api/fields endpoint to create a new text field for you on the fly.textarea
Create new custom fields
A bulk-creation tool. Enter one field name per line (e.g.,
Job Title). Flex Forms will create them all as text fields in MailerLite during the next sync. You can then map to them using the generated key.remote_select
Available fields (reference)
A read-only helper. Shows a live list of all your MailerLite fields (including their required keys and data types like
text, date, or number) for easy copy/pasting.Consent & Opt-in Status
select
default:"active"
Subscriber status
Controls the subscriber’s exact opt-in state when injected into MailerLite.Options:
active: The user is fully opted-in and ready to receive emails immediately.unconfirmed: Triggers Double Opt-in. MailerLite will send them an automated confirmation email. They won’t receive marketing until they click the link in that email.unsubscribed: Explicitly blocks the user from receiving emails (useful for GDPR suppression lists).