diff --git a/modules/rinbox/agent-notify.ts b/modules/rinbox/agent-notify.ts
index dc574af..97c2b99 100644
--- a/modules/rinbox/agent-notify.ts
+++ b/modules/rinbox/agent-notify.ts
@@ -18,11 +18,13 @@ async function getSmtpTransport() {
 	try {
 		const nodemailer = await import("nodemailer");
 		const createTransport = (nodemailer as any).default?.createTransport || nodemailer.createTransport;
+		const isInternal = SMTP_HOST.includes('mailcow') || SMTP_HOST.includes('postfix');
 		_transport = createTransport({
 			host: SMTP_HOST,
-			port: SMTP_PORT,
-			secure: SMTP_PORT === 465,
-			auth: SMTP_USER ? { user: SMTP_USER, pass: SMTP_PASS } : undefined,
+			port: isInternal ? 25 : SMTP_PORT,
+			secure: !isInternal && SMTP_PORT === 465,
+			...(isInternal ? {} : SMTP_USER ? { auth: { user: SMTP_USER, pass: SMTP_PASS } } : {}),
+			tls: { rejectUnauthorized: false },
 		});
 		return _transport;
 	} catch (e) {
diff --git a/modules/rinbox/mod.ts b/modules/rinbox/mod.ts
index ebf8751..c43729a 100644
--- a/modules/rinbox/mod.ts
+++ b/modules/rinbox/mod.ts
@@ -50,13 +50,15 @@ async function getSmtpTransport() {
 	try {
 		const nodemailer = await import("nodemailer");
 		const createTransport = (nodemailer as any).default?.createTransport || nodemailer.createTransport;
+		const isInternal = SMTP_HOST.includes('mailcow') || SMTP_HOST.includes('postfix');
 		_smtpTransport = createTransport({
 			host: SMTP_HOST,
-			port: SMTP_PORT,
-			secure: SMTP_PORT === 465,
-			auth: SMTP_USER ? { user: SMTP_USER, pass: SMTP_PASS } : undefined,
+			port: isInternal ? 25 : SMTP_PORT,
+			secure: !isInternal && SMTP_PORT === 465,
+			...(isInternal ? {} : SMTP_USER ? { auth: { user: SMTP_USER, pass: SMTP_PASS } } : {}),
+			tls: { rejectUnauthorized: false },
 		});
-		console.log(`[Inbox] SMTP transport configured: ${SMTP_HOST}:${SMTP_PORT}`);
+		console.log(`[Inbox] SMTP transport configured: ${SMTP_HOST}:${isInternal ? 25 : SMTP_PORT}`);
 		return _smtpTransport;
 	} catch (e) {
 		console.error("[Inbox] Failed to create SMTP transport:", e);
diff --git a/modules/rpubs/mod.ts b/modules/rpubs/mod.ts
index 117287d..f00627d 100644
--- a/modules/rpubs/mod.ts
+++ b/modules/rpubs/mod.ts
@@ -29,15 +29,19 @@ let _smtpTransport: Transporter | null = null;
 
 function getSmtpTransport(): Transporter | null {
 	if (_smtpTransport) return _smtpTransport;
-	if (!process.env.SMTP_PASS) return null;
+	const host = process.env.SMTP_HOST || "mail.rmail.online";
+	const isInternal = host.includes('mailcow') || host.includes('postfix');
+	if (!process.env.SMTP_PASS && !isInternal) return null;
 	_smtpTransport = createTransport({
-		host: process.env.SMTP_HOST || "mail.rmail.online",
-		port: Number(process.env.SMTP_PORT) || 587,
-		secure: Number(process.env.SMTP_PORT) === 465,
-		auth: {
-			user: process.env.SMTP_USER || "noreply@rmail.online",
-			pass: process.env.SMTP_PASS,
-		},
+		host,
+		port: isInternal ? 25 : (Number(process.env.SMTP_PORT) || 587),
+		secure: !isInternal && Number(process.env.SMTP_PORT) === 465,
+		...(isInternal ? {} : {
+			auth: {
+				user: process.env.SMTP_USER || "noreply@rmail.online",
+				pass: process.env.SMTP_PASS!,
+			},
+		}),
 		tls: { rejectUnauthorized: false },
 	});
 	return _smtpTransport;
diff --git a/modules/rschedule/mod.ts b/modules/rschedule/mod.ts
index c0bd8cf..45ceb48 100644
--- a/modules/rschedule/mod.ts
+++ b/modules/rschedule/mod.ts
@@ -52,15 +52,19 @@ let _smtpTransport: Transporter | null = null;
 
 function getSmtpTransport(): Transporter | null {
 	if (_smtpTransport) return _smtpTransport;
-	if (!process.env.SMTP_PASS) return null;
+	const host = process.env.SMTP_HOST || "mail.rmail.online";
+	const isInternal = host.includes('mailcow') || host.includes('postfix');
+	if (!process.env.SMTP_PASS && !isInternal) return null;
 	_smtpTransport = createTransport({
-		host: process.env.SMTP_HOST || "mail.rmail.online",
-		port: Number(process.env.SMTP_PORT) || 587,
-		secure: Number(process.env.SMTP_PORT) === 465,
-		auth: {
-			user: process.env.SMTP_USER || "noreply@rmail.online",
-			pass: process.env.SMTP_PASS,
-		},
+		host,
+		port: isInternal ? 25 : (Number(process.env.SMTP_PORT) || 587),
+		secure: !isInternal && Number(process.env.SMTP_PORT) === 465,
+		...(isInternal ? {} : {
+			auth: {
+				user: process.env.SMTP_USER || "noreply@rmail.online",
+				pass: process.env.SMTP_PASS!,
+			},
+		}),
 		tls: { rejectUnauthorized: false },
 	});
 	return _smtpTransport;
diff --git a/server/notification-service.ts b/server/notification-service.ts
index bf901a7..b9b7a77 100644
--- a/server/notification-service.ts
+++ b/server/notification-service.ts
@@ -43,15 +43,16 @@ let _smtpTransport: any = null;
 
 async function getSmtpTransport() {
   if (_smtpTransport) return _smtpTransport;
-  if (!SMTP_PASS) return null;
+  const isInternal = SMTP_HOST.includes('mailcow') || SMTP_HOST.includes('postfix');
+  if (!SMTP_PASS && !isInternal) return null;
   try {
     const nodemailer = await import("nodemailer");
     const createTransport = (nodemailer as any).default?.createTransport || nodemailer.createTransport;
     _smtpTransport = createTransport({
       host: SMTP_HOST,
-      port: SMTP_PORT,
-      secure: SMTP_PORT === 465,
-      auth: SMTP_USER ? { user: SMTP_USER, pass: SMTP_PASS } : undefined,
+      port: isInternal ? 25 : SMTP_PORT,
+      secure: !isInternal && SMTP_PORT === 465,
+      ...(isInternal ? {} : SMTP_USER ? { auth: { user: SMTP_USER, pass: SMTP_PASS } } : {}),
       tls: { rejectUnauthorized: false },
     });
     console.log("[email] SMTP transport configured");
diff --git a/server/spaces.ts b/server/spaces.ts
index 1970a9e..17c8b6e 100644
--- a/server/spaces.ts
+++ b/server/spaces.ts
@@ -2097,17 +2097,23 @@ spaces.post("/:slug/copy-shapes", async (c) => {
 
 let inviteTransport: Transporter | null = null;
 
-if (process.env.SMTP_PASS) {
-	inviteTransport = createTransport({
-		host: process.env.SMTP_HOST || "mail.rmail.online",
-		port: Number(process.env.SMTP_PORT) || 587,
-		secure: Number(process.env.SMTP_PORT) === 465,
-		auth: {
-			user: process.env.SMTP_USER || "noreply@rmail.online",
-			pass: process.env.SMTP_PASS,
-		},
-		tls: { rejectUnauthorized: false },
-	});
+{
+	const host = process.env.SMTP_HOST || "mail.rmail.online";
+	const isInternal = host.includes('mailcow') || host.includes('postfix');
+	if (process.env.SMTP_PASS || isInternal) {
+		inviteTransport = createTransport({
+			host,
+			port: isInternal ? 25 : (Number(process.env.SMTP_PORT) || 587),
+			secure: !isInternal && Number(process.env.SMTP_PORT) === 465,
+			...(isInternal ? {} : {
+				auth: {
+					user: process.env.SMTP_USER || "noreply@rmail.online",
+					pass: process.env.SMTP_PASS!,
+				},
+			}),
+			tls: { rejectUnauthorized: false },
+		});
+	}
 }
 
 // ── Enhanced invite by email (with token + role) ──