Allow self signed cert for stalwart

.env.example

@@ -28,6 +28,10 @@ SMTP_USER=
 SMTP_PASS=
 CONTACT_TO=contact@gregkilmer.com
 SMTP_FROM="Greg's Site <no-reply@gregkilmer.com>"
+# Set to "true" to accept a self-signed TLS certificate on the SMTP connection.
+# Only enable when the relay is on a trusted private network (e.g. the homelab
+# Docker network) and presents a self-signed cert. Defaults to false (verify).
+SMTP_ALLOW_SELFSIGNED=
 
 # Optional webhook fallback (JSON POST). Only used if SMTP_HOST is unset.
 # CONTACT_WEBHOOK_URL=

docs/DEPLOYMENT.md

@@ -25,6 +25,7 @@ delivery, set **either** SMTP vars **or** `CONTACT_WEBHOOK_URL` (see
 | `SITE_URL`                                            | Canonical URL for metadata                | `https://gregkilmer.com` |
 | `SMTP_HOST` / `SMTP_PORT` / `SMTP_USER` / `SMTP_PASS` | SMTP relay                                | unset                    |
 | `SMTP_FROM`                                           | From address for outgoing mail            | derived from `SITE_URL`  |
+| `SMTP_ALLOW_SELFSIGNED`                               | Accept self-signed cert (internal hop)    | `false`                  |
 | `CONTACT_TO`                                          | Inbox that receives submissions           | `contact@gregkilmer.com` |
 | `CONTACT_WEBHOOK_URL`                                 | JSON webhook fallback (Discord/Slack/n8n) | unset                    |
 | `CONTACT_RATE_LIMIT` / `CONTACT_RATE_WINDOW_MIN`      | Per-IP rate limit                         | `5` / `15`               |
@@ -123,6 +124,23 @@ not `gmail.com` — SPF on a domain you don't own will reject or sink the mail.
 Test delivery + spam score with [mail-tester.com](https://www.mail-tester.com/)
 (send a form submission to the unique address it gives you).
 
+#### Self-signed certificates on an internal relay
+
+If the SMTP relay (e.g. Stalwart) is on the same private Docker network as the
+site container and presents a self-signed TLS certificate, nodemailer's default
+certificate verification will reject the connection with
+`Error: self-signed certificate` (`code: ESOCKET`). For a trusted internal hop
+that never traverses an untrusted network, set:
+
+```
+SMTP_ALLOW_SELFSIGNED=true
+```
+
+This disables TLS certificate verification for the SMTP connection only. It is
+`false` by default; only enable it when the relay is on a trusted private
+network. For a relay reachable over the public internet, prefer installing a
+real certificate (Let's Encrypt) on the relay instead.
+
 ### Cloudflare Turnstile (bot protection)
 
 The form includes an invisible Cloudflare Turnstile challenge. To enable it:

src/pages/api/contact.ts

@@ -167,11 +167,20 @@ async function deliver(msg: Message): Promise<boolean> {
     const nodemailer = (await import('nodemailer')).default;
     const port = Number(smtpPort() ?? 587);
     const user = smtpUser();
+    // Accept self-signed certificates when explicitly opted in. Intended for
+    // internal homelab hops where the SMTP relay (e.g. Stalwart on the same
+    // Docker network) presents a self-signed cert and the connection never
+    // traverses an untrusted network. Defaults to false so production-grade
+    // TLS verification is the default; the override is a deliberate choice.
+    const allowSelfSigned = env('SMTP_ALLOW_SELFSIGNED') === 'true';
     const transport = nodemailer.createTransport({
       host,
       port,
       secure: port === 465,
       auth: user ? { user, pass: smtpPass() } : undefined,
+      ...(allowSelfSigned
+        ? { tls: { rejectUnauthorized: false } }
+        : {}),
     });
     const hostname = (() => {
       try {