You can send with SMTPfast through either its REST API or its SMTP bridge, then inspect the provider-recorded events to find out whether the request was accepted and what happened afterward. A delivered event is not proof that the message reached the recipient’s inbox or was read.
Before you send: verify the sender and prepare credentials
Both sending methods use SMTPfast’s email pipeline. Before using either one, verify the sending domain and create an API key with the permissions the task requires. For sending, the key needs the email:send scope. If you also want to query the Logs API, that key must additionally have logs:read, which is not enabled by default.
Keep the API key private. For the SMTP bridge, it serves as the SMTP password; for the REST API, send it as a bearer token. Use the SMTPfast dashboard’s Logs page for a manual history check if you do not want to grant your application log-reading access.
Which SMTPfast sending method should you use?
| Method | Best fit | Credentials and setup | How to track the message |
|---|---|---|---|
| REST API | An application that can make HTTP requests and send JSON. | Authorization: Bearer <API key>; JSON fields include from, to, subject, and html and/or text. The sender must use a verified domain. |
Save the email ID returned by a successful send, then look up that message by ID. |
| SMTP bridge | An application or mail library that already supports SMTP submission. | Host smtp.smtpfa.st; port 587 or 2525; STARTTLS; username smtpfast; password is the SMTPfast API key with the email:send scope. |
Use the dashboard Logs page or query Logs API history with suitable filters; capture the message ID if your integration exposes it. |
SMTPfast documents port 2525 for environments that block standard SMTP submission ports. Its SMTP bridge uses the same verified domains, rate limits, suppression checks, queueing, logs, and webhooks as the HTTP API.
#1 Best Overall
Way 1: Send an email with the SMTPfast REST API
Make a POST request to https://smtpfa.st/api/v1/emails with your API key in the authorization header and a JSON body containing the sender, recipient, subject, and message body. Include html, text, or both.
curl -X POST https://smtpfa.st/api/v1/emails
-H "Authorization: Bearer YOUR_API_KEY"
-H "Content-Type: application/json"
-d '{
"from": "you@your-verified-domain.com",
"to": "recipient@example.com",
"subject": "A test message",
"text": "This is a test email."
}'Replace the sample addresses and key with your own values. The sender domain must be verified with SMTPfast. A successful send returns an email ID: save it rather than relying only on the immediate response, because you will use it to inspect that message’s later details and events.
Rank #2
Way 2: Send through SMTPfast’s SMTP bridge
In your SMTP-capable application or mail library, enter the connection settings below. Choose either documented submission port; use STARTTLS for the connection security setting.
| SMTP setting | Value |
|---|---|
| Host | smtp.smtpfa.st |
| Port | 587 or 2525 |
| Security | STARTTLS |
| Username | smtpfast |
| Password | Your SMTPfast API key with the email:send scope |
Set the message’s From address to a sender on a verified domain. If the standard SMTP submission port is blocked in your environment, SMTPfast documents port 2525 as an alternative. The bridge applies the same documented sending controls and records as API sends.
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There are three different questions to separate: did SMTPfast accept the send request, what later event did SMTPfast record, and did the recipient actually see the message in an inbox? A successful API response and an email ID address the first question. The event history helps answer the second. SMTPfast’s recorded events do not independently prove inbox placement or that the recipient read the message.
Look up one API-sent email by ID
After a successful API send, request GET /v1/emails/:id, substituting the returned ID for :id. The response provides message details and its events, allowing you to follow the recorded history for that specific send.
Rank #4
Inspect broader history in Logs
For a quick manual check, open the Logs page in the SMTPfast dashboard. For application-driven investigation or team history, use GET /v1/logs. The Logs API supports filters for event type, date range, exact recipient, sending domain, tag, and email ID, and uses cursor pagination. Requests to this API require the non-default logs:read scope.
SMTPfast describes the Logs API as the place to reconcile a message’s lifecycle, including internal steps that do not reach a webhook: “The log is the full lifecycle history, including the internal steps (queued, sending, retrying) that never reach a webhook, so it is the place to check what happened to a message and to reconcile after a webhook outage.”
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Events can describe intermediate processing, an outcome, or recipient interaction. Read them as SMTPfast’s record of the lifecycle—not as equivalent claims about what appeared in a person’s mailbox.
| Event | What it tells you |
|---|---|
queued, sending, retrying |
Internal or intermediate processing states. These help show that processing is underway or being retried; they are not final proof of delivery. |
sent |
SMTPfast recorded a sent event. Do not treat it as proof of inbox visibility. |
delivered |
SMTPfast recorded a delivery event. It does not establish that the message appeared in the inbox rather than another folder, or that it was read. |
delivery_delayed |
SMTPfast recorded a delivery delay; inspect subsequent events for the later status. |
bounced, complained, failed, suppressed |
These indicate a problem, rejection, complaint, or suppression state. Logs may include useful failure details such as bounce type or subtype, or an error message. |
opened, clicked, unsubscribed |
These are additional recipient-related events recorded by the service. They are distinct from proof of inbox placement. |
When to use logs versus webhooks
Use Logs when you need to inspect a message after the fact, search across messages, or recover the full recorded lifecycle. Use webhooks when an application needs to react to supported event changes. Because some internal steps do not reach webhooks, logs remain useful for reconciliation. Check SMTPfast’s current webhook documentation for supported event details and delivery behavior before building around a particular payload or guarantee.
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