diff --git a/src/lib/email.ts b/src/lib/email.ts
index fa260ac..8c3941e 100644
--- a/src/lib/email.ts
+++ b/src/lib/email.ts
@@ -1,4 +1,4 @@
-import { createTransport } from "nodemailer";
+import { createTransport, type Transporter } from "nodemailer";
 import SMTPTransport from "nodemailer/lib/smtp-transport";
 
 import type { Options } from "nodemailer/lib/mailer";
@@ -24,6 +24,27 @@ export function constructEmailHtml(props: Email) {
   return `<div>${escapeHtml(props.message)}</div>`;
 }
 
+// Cached for the process lifetime: config comes from the environment and
+// does not change between requests.
+let cachedTransporter: Transporter | null = null;
+
+function getTransporter(port: number, secure: boolean): Transporter {
+  if (!cachedTransporter) {
+    cachedTransporter = createTransport({
+      host: process.env.EMAIL_HOST || import.meta.env.EMAIL_HOST,
+      port,
+      secure,
+      // Refuse plaintext fallback on submission ports (e.g. 587, 2525).
+      requireTLS: !secure,
+      auth: {
+        user: process.env.EMAIL_USER || import.meta.env.EMAIL_USER,
+        pass: process.env.EMAIL_PASS || import.meta.env.EMAIL_PASS
+      }
+    } as SMTPTransport.Options);
+  }
+  return cachedTransporter;
+}
+
 export default async function sendContactEmail(props: Email) {
   const port = parseInt(
     process.env.EMAIL_PORT || import.meta.env.EMAIL_PORT || "",
@@ -35,17 +56,11 @@ export default async function sendContactEmail(props: Email) {
     throw new Error("Email transport is not configured.");
   }
 
-  const transporter = createTransport({
-    host: process.env.EMAIL_HOST || import.meta.env.EMAIL_HOST,
-    port,
-    secure:
-      process.env.EMAIL_SECURE === "true" ||
-      import.meta.env.EMAIL_SECURE === "true",
-    auth: {
-      user: process.env.EMAIL_USER || import.meta.env.EMAIL_USER,
-      pass: process.env.EMAIL_PASS || import.meta.env.EMAIL_PASS
-    }
-  } as SMTPTransport.Options);
+  const secure =
+    process.env.EMAIL_SECURE === "true" ||
+    import.meta.env.EMAIL_SECURE === "true";
+
+  const transporter = getTransporter(port, secure);
 
   if (!props.html) {
     props.html = constructEmailHtml(props);
diff --git a/src/pages/api/email/contact.ts b/src/pages/api/email/contact.ts
index 291b7a4..8aa6be9 100644
--- a/src/pages/api/email/contact.ts
+++ b/src/pages/api/email/contact.ts
@@ -20,10 +20,19 @@ function isRateLimited(ip: string): boolean {
     (t) => now - t < RATE_WINDOW_MS
   );
   if (history.length >= RATE_MAX) {
+    recentSends.set(ip, history);
     return true;
   }
   history.push(now);
   recentSends.set(ip, history);
+  // Prune expired entries so the map cannot grow without bound.
+  if (recentSends.size > 500) {
+    for (const [key, times] of recentSends) {
+      if (!times.some((t) => now - t < RATE_WINDOW_MS)) {
+        recentSends.delete(key);
+      }
+    }
+  }
   return false;
 }
 
@@ -36,10 +45,8 @@ function json(message: string, status: number, statusText: string): Response {
 }
 
 export const POST: APIRoute = async ({ request, clientAddress }) => {
-  const ip =
-    request.headers.get("x-forwarded-for")?.split(",")[0]?.trim() ||
-    clientAddress ||
-    "unknown";
+  // Prefer the socket address: x-forwarded-for is client-controlled.
+  const ip = clientAddress || "unknown";
   if (isRateLimited(ip)) {
     return json(
       "Too many messages sent. Please try again later.",
@@ -48,7 +55,13 @@ export const POST: APIRoute = async ({ request, clientAddress }) => {
     );
   }
 
-  const data = await request.formData();
+  let data: FormData;
+  try {
+    data = await request.formData();
+  } catch (error) {
+    console.error("Contact form parse failed:", error);
+    return json("Invalid request.", 400, "Bad Request");
+  }
   const email = (data.get("email") as string | null)?.trim() ?? "";
   const subject = (data.get("subject") as string | null)?.trim() ?? "";
   const message = (data.get("message") as string | null)?.trim() ?? "";
@@ -86,6 +99,7 @@ export const POST: APIRoute = async ({ request, clientAddress }) => {
       html
     });
   } catch (error) {
+    console.error("Contact email failed to send:", error);
     return json(
       `Message failed to send with an internal server error. Please contact me directly via a method below.`,
       500,