From Loops to Postal, with the same building blocks

In Domains, Postal shows a few records for whoever manages DNS to copy, and checks them on its own for up to 72 hours. The domain can stay verified on Loops at the same time.

• Going by the names, Postal's records don't collide with Loops'. Copy the values from your own Loops screen and check whether any name is the same before publishing.
• Postal notifies you through the domain.updated webhook when the domain becomes verified. See Domains and DNS.
• Create an API key (it starts with ps_). For systems that only send, use a send-only key restricted to the domain.

In Loops, the call says only who to send to and which transactional email to use: the sender, subject and body live in the email registered there. In Postal the design is similar, with the template in place of the transactional email, but the call is different.

POST https://app.loops.so/api/v1/transactional
Authorization: Bearer <Loops key>
Idempotency-Key: order-10482-shipped
Content-Type: application/json

{
  "email": "[email protected]",
  "transactionalId": "clomzp89u635xl30px7wrl0ri",
  "dataVariables": { "nome": "Ana", "pedido": "10482" }
}

POST https://api.postal.so/emails
Authorization: Bearer ps_your_key
Idempotency-Key: order-10482-shipped
Content-Type: application/json

{
  "from": "Aurora Cosméticos <[email protected]>",
  "to": "[email protected]",
  "template": {
    "id": "order-shipped",
    "variables": { "nome": "Ana", "pedido": "10482" }
  }
}

• In Loops, people who unsubscribed still receive transactional emails. It's the same in Postal: only the suppression list blocks an API send.
• Prefer an SDK? Postal's (Node.js, PHP and Laravel) use this same API. See SDKs and CLI and the emails reference.

Over SMTP, Loops doesn't receive an ordinary email: the message body is a JSON with the transactionalId, the recipient's address and the template data (in the documentation's Laravel example, the address from Mail::to() isn't used for delivery). Postal's SMTP delivers the message as it arrives, with the subject, the HTML and the email's own recipients.

{
  "transactionalId": "clomzp89u635xl30px7wrl0ri",
  "email": "[email protected]",
  "dataVariables": { "loginUrl": "https://exemplo.com.br/entrar?code=482913" }
}

- MAIL_HOST=smtp.loops.so- MAIL_PORT=587- MAIL_USERNAME=loops- MAIL_PASSWORD=<chave de API do Loops>- MAIL_ENCRYPTION=tls+ MAIL_SCHEME=smtps+ MAIL_HOST=smtp.postal.so+ MAIL_PORT=465+ MAIL_USERNAME=postal+ MAIL_PASSWORD=ps_sua_chave

• In Laravel, this means replacing the text view that built the JSON with a view holding the email's HTML, and passing the subject in the Envelope. The address from Mail::to() now takes effect.
• In Postal, authentication (AUTH PLAIN or AUTH LOGIN) always comes after TLS. SMTP has no tags or scheduling.
• SMTP sends follow the same rules as the API (verified domain, quotas and suppression) and show up in Emails and Logs. See the SMTP guide.

Events play the same role in both: they tell the platform what happened in your product and start flows. In Postal, a single POST /events also registers or updates the person before starting the automations.

POST https://app.loops.so/api/v1/events/send
Authorization: Bearer <Loops key>
Idempotency-Key: order-10482-paid
Content-Type: application/json

{
  "email": "[email protected]",
  "eventName": "order_paid",
  "eventProperties": { "total": 289.9 },
  "plano": "pro"
}

POST https://api.postal.so/events
Authorization: Bearer ps_your_key
Idempotency-Key: order-10482-paid
Content-Type: application/json

{
  "name": "order_paid",
  "contact": { "email": "[email protected]" },
  "properties": { "total": 289.9 },
  "contact_properties": { "plano": "pro" }
}

• An event without contact is recorded but doesn't start automations. With a new email, Postal creates the contact, notifies the contact.created webhook and starts the contact-created automations.
• An address on the suppression list never becomes a contact: the response is 422 email_suppressed.
• The Node.js and PHP SDKs (events.send) and the CLI (postal events send) send events. See the events reference.

Flows don't carry over on their own. The good news is that the blocks are almost the same, so the conversion is just renaming: open each Loops workflow and build the equivalent in Automations.

• Each contact enters once by default (reentry: "once"). To enter on every trigger, use every_time.
• Campaigns and saved segments (saved segments) are also rebuilt: campaigns in Campaigns and segments as dynamic segments. Campaigns that were already sent aren't imported.
• Imports don't start automations unless you turn that option on. Review who would enter before you activate it. See Automations.

Postal doesn't convert emails from another platform. Paste the HTML into the editor or send it through POST /templates. What changes is how you write the variables.

POST https://api.postal.so/templates
Authorization: Bearer ps_your_key
Content-Type: application/json

{
  "name": "Access code",
  "alias": "access-code",
  "subject": "Your access code",
  "html": "<p>To sign in, <a href=\"{{{loginUrl}}}\">click here</a>.</p>",
  "variables": [{ "key": "loginUrl" }]
}

• Variable names accept letters, numbers and _, up to 50 characters. Declare in variables the ones that have a default value.
• The template also stores the default sender and subject (from, subject), which apply when the send doesn't provide its own.
• See the templates reference; the plan sets how many templates the team has.

Signature verification is the same on both: the documentation for each describes the headers webhook-id, webhook-timestamp and webhook-signature and an HMAC-SHA256, in Base64, of id.timestamp.corpo, with the whsec_… secret. Your verification code should keep working, just with the new endpoint's secret. What changes are the event names and bodies.

• Create the endpoint in Webhooks (dashboard or POST /webhooks), choose the events and store the signing_secret. See the signature verification.
• Remove the Loops webhook only after switching all your traffic: emails that still go out through Loops keep generating events.

In Loops' Audience, open the ••• menu at the corner of the filter box and choose Download. To export just one group, apply the filters first. The CSV has one column per contact property, the default ones and yours. In Postal, the import is under Audience, Import CSV.

• Subscribed is the inverse of Unsubscribed. Create an Unsubscribed column with sim where Subscribed is false and não where it is true. Or download two files, filtering by Subscribed, and import the unsubscribed one with sim on every row.
• Suppressed: Loops' documentation only describes looking up one address at a time (GET /v1/contacts/suppression?email=). To separate the suppressed from those who unsubscribed by choice, query each address in the unsubscribed file (the limit is 10 requests per second) and put the suppressed ones on the suppression list with POST /suppressions/batch/add, 100 per request, before importing contacts.
• Lists: Loops doesn't document whether the CSV includes list membership. If it doesn't, export one list per file. Lists become topics (public or private, as there): import each file selecting the topic in Subscribe to topics. That field subscribes every contact in the file.
• Properties: the types are the same (text, number, yes/no and date). Source, User Group and Notes become properties you create beforehand, because the import doesn't create new properties. Dates in the 2026-10-28 format work.
• Plan limit: in Loops, unsubscribed contacts don't count toward your plan. In Postal, unsubscribed contacts take up a slot in the contact limit (1,000 on Free; 5,000 on Pro; 50,000 on Scale). Addresses on the suppression list don't. See Pricing.
• Leave the Trigger automations option off. Contacts that already exist are updated by email, empty cells don't erase values, and each file can be up to 20 MB.
• Before sending, run the list through Email validation.

Switch one flow at a time, with Loops still on. Start with the test addresses and with yourself, compare deliveries and bounces over the first few days, and only then move the rest.