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Posthorn

Multi-form site

A site that has more than one form. The contact form goes to you@. The feedback form goes to product@. The careers form goes to hiring@ with attachments-disabled and a sterner rate limit. All three are independent endpoints on the same Posthorn container.

At the end: three /api/* paths in one Posthorn config, each with its own template, recipients, and rate limit. Rate-limiting /api/contact doesn’t affect /api/careers. Different forms can use different sending identities.

Prerequisites

Section titled “Prerequisites”

Same as Contact form — a verified Postmark sender domain, a server token, a Docker host, a reverse proxy in front.

Walkthrough

Section titled “Walkthrough”

  1. Write a multi-endpoint posthorn.toml.

    [logging]
    level = "info"
    format = "json"
    

    # ----- Contact form -----------------------------------------------
    

    [[endpoints]]
    path = "/api/contact"
    to = ["you@yourdomain.com"]
    from = "Contact Form <noreply@yourdomain.com>"
    reply_to_email_field = "email"
    honeypot = "_gotcha"
    allowed_origins = ["https://yourdomain.com", "https://www.yourdomain.com"]
    required = ["name", "email", "message"]
    subject = "Contact: {{.name}}"
    body = """
    From: {{.name}} <{{.email}}>
    

    {{.message}}
    """
    redirect_success = "/contact/thanks/"
    

    [endpoints.transport]
    type = "postmark"
    

    [endpoints.transport.settings]
    api_key = "${env.POSTMARK_CONTACT_KEY}"
    

    [endpoints.rate_limit]
    count = 5
    interval = "1m"
    

    # ----- Feedback form ----------------------------------------------
    

    [[endpoints]]
    path = "/api/feedback"
    to = ["product@yourdomain.com"]
    from = "Product Feedback <noreply@yourdomain.com>"
    reply_to_email_field = "email"
    honeypot = "_trap"
    allowed_origins = ["https://yourdomain.com", "https://www.yourdomain.com"]
    required = ["category", "feedback"]
    email_field = "email"
    subject = "Feedback ({{.category}}): {{.feedback}}"
    body = """
    Category: {{.category}}
    Reporter: {{.email}}
    

    {{.feedback}}
    """
    redirect_success = "/feedback/thanks/"
    

    [endpoints.transport]
    type = "postmark"
    

    [endpoints.transport.settings]
    api_key = "${env.POSTMARK_FEEDBACK_KEY}"
    

    [endpoints.rate_limit]
    count = 10
    interval = "1m"
    

    # ----- Careers form -----------------------------------------------
    

    [[endpoints]]
    path = "/api/careers"
    to = ["hiring@yourdomain.com"]
    from = "Careers Inbox <noreply@yourdomain.com>"
    reply_to_email_field = "email"
    honeypot = "_decoy"
    allowed_origins = ["https://yourdomain.com", "https://www.yourdomain.com"]
    required = ["name", "email", "role", "linkedin"]
    subject = "Application: {{.name}} for {{.role}}"
    body = """
    Name: {{.name}}
    Email: {{.email}}
    Role: {{.role}}
    LinkedIn: {{.linkedin}}
    """
    redirect_success = "/careers/thanks/"
    

    [endpoints.transport]
    type = "postmark"
    

    [endpoints.transport.settings]
    api_key = "${env.POSTMARK_CAREERS_KEY}"
    

    [endpoints.rate_limit]
    count = 2
    interval = "1h"

  2. Decide on transport tokens.

    The example above uses three distinct env vars (POSTMARK_CONTACT_KEY, POSTMARK_FEEDBACK_KEY, POSTMARK_CAREERS_KEY). You have two patterns to choose between:

    • One server token, three endpoints. Simplest. Same api_key = "${env.POSTMARK_API_KEY}" in all three. All forms send from the same Postmark server. Per-server statistics in Postmark conflate the three forms.
    • Three server tokens, three Postmark servers. Better isolation. Each form has its own server in Postmark with its own DomainKeys Identified Mail (DKIM) signature, its own stats, its own rate limit upstream. Bounce one server’s reputation, the other two are unaffected.

    For low-volume sites, one token is fine. For mixed traffic shapes (contact form sees real humans, careers form sees recruiter spam, feedback form sees bug reports), separate tokens earn their keep.

  3. .env.

    Terminal window
    # One-token shape:
    # POSTMARK_API_KEY=your-token
    

    # Or three-token shape:
    POSTMARK_CONTACT_KEY=your-contact-server-token
    POSTMARK_FEEDBACK_KEY=your-feedback-server-token
    POSTMARK_CAREERS_KEY=your-careers-server-token

  4. Reverse-proxy all three paths.

    For Caddy:

    yourdomain.com {
        @forms path /api/contact /api/feedback /api/careers
        handle @forms {
            reverse_proxy 127.0.0.1:8080
        }
    

        handle {
            root * /var/www/yourdomain.com
            file_server
        }
    }

    For nginx, use a location ~ ^/api/(contact|feedback|careers)$ match — see the Reverse proxy page.

  5. Restart.

    Terminal window
    docker compose restart posthorn
    docker compose logs --tail 20 posthorn

    Expect:

    {"time":"...","level":"INFO","msg":"endpoint registered","path":"/api/contact","transport":"postmark","recipients":1}
    {"time":"...","level":"INFO","msg":"endpoint registered","path":"/api/feedback","transport":"postmark","recipients":1}
    {"time":"...","level":"INFO","msg":"endpoint registered","path":"/api/careers","transport":"postmark","recipients":1}
    {"time":"...","level":"INFO","msg":"http ingress listening","addr":":8080"}

  6. Wire the three forms into your site. Each form’s action="/api/..." points at the matching endpoint. Different honeypot field names per form (so a generic bot scanner can’t pattern-match across them).

What’s per-endpoint and what’s global

Section titled “What’s per-endpoint and what’s global”
ConcernScopeNotes
Rate limitPer-endpoint, per-IP/api/contact rate limit doesn’t affect /api/careers
RecipientsPer-endpointEach form goes where it should
Templates (subject, body)Per-endpointIndependent for each form
Honeypot field namePer-endpointUse different names for each form to avoid pattern-matched bot scrapers
allowed_originsPer-endpointTypically the same list for all forms on a site
Transport settingsPer-endpointOne Postmark token or three — your call
[logging]GlobalOne log stream for the whole container
HTTP listener portGlobalOne :8080, all endpoints multiplexed by path

Common gotchas

Section titled “Common gotchas”
SymptomLikely causeFix
Form on /feedback goes to the wrong inboxEndpoints share path prefixes; Posthorn does exact-match routingMake sure each endpoint’s path is exact (/api/feedback, not /api/feedback/ — the trailing slash matters)
Rate limit on the careers endpoint blocks legitimate applicantsThe count = 2 per hour example is conservative; tune to your actual volumeBump count up or shorten interval
Different from addresses but mail all looks the same in GmailGmail collapses threads by participants — three forms going from the same noreply@ will thread togetherUse distinct from display names (Contact Form, Product Feedback, Careers Inbox) so the From column distinguishes them
Bots discover the careers endpoint via path enumerationThe endpoint paths are guessable; that’s by design (operator-visible)Tighter rate limit + stricter required fields (e.g., requiring a LinkedIn URL filters obvious spam)

Where to go next

Section titled “Where to go next”