Migrate from MailerLite to Unitpost

Before you start

• A MailerLite API token: Integrations → MailerLite API → Generate new token. MailerLite shows it once.
• Leave IP restrictions off for this token. MailerLite lets you limit a token to certain IP addresses, and a restricted token refuses the importer.
• A current MailerLite account. Accounts created before March 2022 that still run on MailerLite Classic use a separate API and key, which the importer doesn't read.
• MailerLite tokens have no read-only setting and stop working if the user who made them leaves the account. The importer only reads; delete the token when the move is done.
• A Unitpost API key for your app with emails:send, plus contacts:write and segments:write if your signup form adds contacts, created in API keys.
• A second Unitpost key for the migration steps, with templates:write and webhooks:manage, saved as UNITPOST_MIGRATION_KEY. Keep it out of your app and revoke it once the move is done.
• Access to your DNS host.

The cut-over plan

MailerLite keeps sending until the last step, so there is no gap in delivery.

1. 1

   Run the Migration Assistant

   Paste the token in Settings → Migration. The preview counts subscribers by status, lists the unconfirmed ones it leaves out, and shows which campaigns arrive as plain text. Suppressions are written before contacts, so bounced and junk addresses land unsubscribed.

2. 2

   Verify your domain

   Open Domains, add any domain the importer didn't find, and publish the records shown: MX and SPF on unitpost.<your domain> and a DKIM TXT under _domainkey. They don't replace MailerLite's records, so both stay authenticated while you move. Keep your single _dmarc record.

3. 3

   Rebuild designs from the plain-text drafts

   Each campaign arrives as a plain-text draft with its subject. Rebuild the layout in the visual editor, or paste your own HTML in code mode. {$name} became {{first_name}}, {$last_name} {{last_name}}, {$email} {{email}} and {$unsubscribe} {{unsubscribe_url}}; |default('…') fallbacks are dropped, and {$url}, {$forward} and {$preferences} stay for you to replace. Publish with PATCH /api/v1/email/templates/{id}.

4. 4

   Point signups at Unitpost

   MailerLite forms, landing pages and websites keep adding subscribers to MailerLite. Send signups from your own form with POST /api/v1/contacts, and add the contact to the segment that replaced each group. MailerLite's create call updates an existing subscriber; here an existing contact answers 409, and PATCH /api/v1/contacts/{id or email} updates it.

   signup.ts

   // Before: MailerLite
   await fetch("https://connect.mailerlite.com/api/subscribers", {
     method: "POST",
     headers: { Authorization: "Bearer " + process.env.MAILERLITE_API_KEY, "content-type": "application/json" },
     body: JSON.stringify({
       email: "user@example.com",
       fields: { name: "Ada", last_name: "Lovelace" },
       groups: [GROUP_ID],
     }),
   });
   
   // After: Unitpost
   import { Unitpost } from "unitpost";
   const unitpost = new Unitpost(process.env.UNITPOST_API_KEY);
   const { error } = await unitpost.contacts.create({
     email: "user@example.com",
     first_name: "Ada",
     last_name: "Lovelace",
   });
   // 409 conflict: the contact already exists. MailerLite's call upserts; update with contacts.update.
   if (error && error.code !== "conflict") throw new Error(error.message);
   // A group became a static segment.
   await unitpost.segments.addMember("seg_123", { contact: "user@example.com" });

5. 5

   Re-key and enable webhooks

   MailerLite signs each delivery with a Signature header, an HMAC-SHA256 of the body. Unitpost signs with a whsec_ secret in svix-id, svix-timestamp and svix-signature. Rotate the secret in Webhooks to see it, update your handler, then set status to enabled.

6. 6

   Test, move traffic, then delete the token

   Send each template with POST /api/v1/email/templates/{id}/test-send and fire POST /api/v1/webhooks/{id}/test at each endpoint. Send your next campaign from Unitpost to a small segment first, then to everyone, and delete the MailerLite token.

Before you cancel MailerLite

• Export subscribers as CSV, including unconfirmed ones, which the importer leaves out.
• Save the designs you still use; MailerLite's API can't hand them over.
• Write down each automation, with its trigger, steps and delays.
• Move your forms, landing pages and websites, or keep MailerLite for them.
• Delete MailerLite's DNS records once no mail goes through MailerLite. Keep _dmarc and Unitpost's records.
• Delete the MailerLite API token you used for the import.

Facts about MailerLite checked 2026-11-05. Providers change their APIs and plans; check their docs before you rely on a detail.