Automate email on your own SMTP relay
If your compliance posture, sovereignty requirements, or budget says "no third-party ESP", FlowingMail still works. Point the send action at your Postfix, Exim, Haraka, or managed SMTP relay - keep the sending inside your perimeter.
Why SMTP + FlowingMail
For teams that can't (or don't want to) route traffic through Resend/SendGrid/Mailgun/SES - FlowingMail still adds the workflow layer.
- Send through any SMTP server you control
- STARTTLS / implicit TLS / plain - configurable per sender
- Per-sender concurrency limits and rate caps
- On-prem mail stays on-prem - only metadata crosses the network
- Compatible with compliance-regulated workloads (HIPAA, PCI)
- Mix SMTP with cloud providers - pick the destination per send action
Everything you'd expect, just over SMTP
Visual workflow canvas
Same editor as every other FlowingMail provider - triggers, branches, delays, filters, sends.
Segmentation
Attribute-based filters + groups. Reusable segments across campaigns and flows.
Template editor
HTML + plain-text templates. Variable interpolation, fallback values, live preview.
Delivery & open tracking
Click/open tracking via FlowingMail's tracking domain (optional). Bounces and deferrals parsed from SMTP responses.
TLS & authentication
TLS 1.2+, STARTTLS, LOGIN / PLAIN / CRAM-MD5 auth, client certs for mutual TLS.
VPN / private network friendly
Send through an SMTP relay on a private network - pair with FlowingMail's self-hosted worker for zero-egress delivery.
Three steps to SMTP workflows
Add SMTP credentials
Host, port, username, password (or client cert). Test connection, verify HELO, you're in.
Design the flow
Same canvas: pick triggers, build branches, configure delays, drop sends bound to your SMTP sender.
Send
FlowingMail opens a connection, pipelines commands, and tears it down - per your concurrency / rate settings.
SMTP connection details
FlowingMail supports any standards-compliant SMTP relay. These are the fields you configure per sender.
host: smtp.internal.acme.com
port: 587
security: starttls # starttls | tls | plain
username: [email protected]
password: ${SMTP_PASSWORD}
from_address: [email protected]
from_name: Acme
rate_limit: 100/s
max_concurrency: 16SMTP relay automation - FAQ
Any RFC 5321-compliant SMTP relay: Postfix, Exim, Haraka, OpenSMTPD, Microsoft Exchange, Google Workspace SMTP, or managed relays like Mailjet / Postmark SMTP. If it speaks STARTTLS or implicit TLS, FlowingMail can send through it.
Yes. Upload a client certificate + private key on the sender configuration. Useful for on-prem relays that enforce mTLS.
FlowingMail rewrites links through its tracking domain (optional, per-sender) and injects a 1x1 tracking pixel for open tracking. You can disable both per-sender or per-template.
FlowingMail itself stores email metadata (addresses, template variables, engagement events). If you need zero PHI/PCI in FlowingMail's database, pair with the self-hosted worker so rendering and sending happen inside your perimeter.
Yes. Each send-email node binds to a specific sender. A single flow can route marketing through SES and compliance-sensitive transactional through your internal SMTP relay.
SMTP-level 4xx / 5xx responses are captured and classified. Hard bounces suppress future sends to that contact. For async bounces (NDR messages), point your mailer-daemon forwarder at FlowingMail's ingress endpoint to parse them.
Explore more
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If you prefer Mailgun over raw SMTP.
How the workflow canvas works across providers.
Receipts, alerts, and password resets - perfect for internal SMTP.
Broader platform overview.
Deep dive into the canvas that powers every flow.