TLS-first submission
The public endpoint expects secure submission on port 587 and keeps handshake diagnostics visible to operators.
SMTPKeep your mailer, change four lines
SMTP submission for the mailer you already run
Point existing frameworks, monoliths, alerting tools, and legacy SaaS at Sendix SMTP while inheriting verified-domain checks, queues, webhooks, and direct-MX delivery.
- STARTTLS on port 587
- API key as the password
- Same queue as API sends
- Delivery events still signed
smtp submission
tls.envport 587
SMTP_HOST=smtp.sendix.dev
SMTP_PORT=587
SMTP_USER=sendix
SMTP_PASS=YOUR_API_KEYhandshake
S:220 smtp.sendix.dev ready
C:EHLO app.internal
S:250-STARTTLS
C:STARTTLS
C:AUTH PLAIN ****
S:235 Authentication successful
C:MAIL FROM:<[email protected]>
S:250 queued as 01HXY8
Migration flow
Move the delivery provider first, modernize the code later.
SMTP submission is a compatibility layer for teams that want Sendix delivery without rewriting the mailer today.
01
smtp.sendix.dev
Swap the host
Keep your mailer and update host, port, username, and the API-key password. No new SDK.
02
STARTTLS
Upgrade with STARTTLS
The endpoint expects a secure submission on 587 and reports diagnostics to operators.
03
Verified domain
Enforce trust
Sender-domain checks and credential limits run before a message is ever queued.
04
Events
Track normally
SMTP sends produce the same logs, queue state, metrics, and webhook events as API sends.
Compatibility
A bridge into the platform, not a second place to debug.
SMTP accepts the message, then hands it to the same verification, queue, and event machinery every other Sendix send uses.
Credential scoped
API keys double as SMTP credentials, so rotation and access control stay familiar.
Direct-MX routing
Messages move from SMTP accept into the same Sendix direct-MX worker path.
Same event model
Delivered, bounced, deferred, and complained events do not care whether the source was SMTP or REST.
Drop-in forRails ActionMailerDjangoLaravel MailSpring MailWordPressGrafana Alerts
Protocol transcript
A secure handshake before anything is queued.
Every submission upgrades to TLS, authenticates with your API key, and passes sender-domain checks — then joins the same delivery pipeline as the REST API.
Read the SMTP guidesmtp.sendix.dev:587STARTTLS
S:220 smtp.sendix.dev ready
C:EHLO app.internal
S:250-STARTTLS
C:STARTTLS
C:AUTH PLAIN ****
S:235 Authentication successful
C:MAIL FROM:<[email protected]>
S:250 queued as 01HXY8
Same pricing as the rest of Sendix
SMTP is not a separate add-on.
The free tier includes 25,000 emails per month across API and SMTP. Upgrading changes volume and limits, not the way you submit mail.
FAQ
Practical answers before you re-point the mailer.
Short notes for the questions teams ask when moving an existing SMTP integration to Sendix.
Is SMTP separate from the Email API?
No. SMTP submission enters the same verification, queueing, delivery, and event pipeline as the REST API. It is an entry point, not a second product to debug.
What authentication does SMTP use?
Use your Sendix API key as the SMTP password, with the username shown in the dashboard. Rotating the key rotates the SMTP credential.
Do SMTP sends trigger webhooks?
Yes. Once a message is accepted, SMTP sends use the same signed event model — delivered, bounced, deferred, and complained.
Which tools can point at Sendix SMTP?
Framework mailers, alerting tools, CMS mail, and legacy monoliths that already speak authenticated SMTP can submit without code changes.
Ready to send your first email?
25,000 emails free every month. No credit card required. Upgrade only when you outgrow the free tier — and we will let you know when that time comes.
Managed SaaS platform · Native SMTP engine · SOC 2 in progress