Core concepts
Destinations
A destination is the outbound side of the pipeline the actual provider mailnix dispatches messages to. You can connect as many as you want; routing rules and failover policies decide which one gets each message.
Supported providers
| Provider | Use case | Verification |
|---|---|---|
| SMTP (custom) | Your webhoster's mailserver (Hostpoint, IONOS, OVH, etc.) or self-hosted Postfix. | The destination's from domain must be one you can send for via the SMTP host. We don't check this; the host will. |
| SES | AWS Simple Email Service. | Verify your sending domain in the AWS SES console. |
| Resend | Resend.com API. | Verify your domain via the Resend dashboard. |
| Postmark | Postmark API. | Verify your sender signature in Postmark. |
| Mailgun | Mailgun API. | Verify your domain on Mailgun. |
Webhoster presets
For SMTP, instead of typing the host + port + TLS settings, pick a preset from the catalog. We know the right smtp_host, port, and encryption for these:
cyon, hostpoint, hoststar, infomaniak, ionos, strato, mittwald, all-inkl, ovh, gandi
The preset fills the host/port/TLS fields; you only enter your mailbox username + password. For an unknown webhoster, pick "custom SMTP" and enter the host yourself.
Domain verification
For real-recipient sends (not sandbox), the recipient's mailserver will reject your message if your sending domain doesn't pass at least SPF and ideally also DKIM + DMARC. Three records:
- SPF: a TXT record on your sending domain that says "this list of IPs is authorized to send for me." Example:
v=spf1 include:_spf.mailnix.ch ~all. The exact content depends on the destination provider; we generate it for you. - DKIM: a TXT record on a
*._domainkey.<domain>selector that publishes the public half of a signing key. The provider signs outbound messages; receivers verify the signature against the DNS record. - DMARC: a TXT record on
_dmarc.<domain>that tells receivers what to do when SPF and DKIM both fail. Start withv=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com(monitor mode); tighten top=quarantinethenp=rejectonce you've confirmed clean traffic for a few weeks.
To check the current state of your records, the dashboard surfaces a domain-verification page per destination. The MCP server exposes the same checks via email_domain_verify_status(domain).
Test sends
Once a destination is active, hit the Send test button on its detail page. We send a one-line message to an inspect inbox and show you the captured copy + the SPF/DKIM/DMARC results parsed from the received headers. This is the fastest way to confirm the destination actually works end-to-end.
Capabilities
Each destination advertises a set of capabilities the routing engine checks:
transactional: standard 1:1 sendswebhooks_delivery: the provider reports delivery via webhooks (so we can populateprovider_event_deliveryetc. on the trace)webhooks_bounce: bounce / complaint webhookswebhooks_open/webhooks_click: tracking-pixel + link-tracking webhookstemplates: server-side template variables (Postmark / Mailgun style)attachments: arbitrary-MIME-type attachments
Custom SMTP destinations get transactional only no webhooks (SMTP has no out-of-band mechanism for them) and no template support. Use a cloud provider when you need either.