diff --git a/server/src/nest/notifications/mailer/mailer.service.ts b/server/src/nest/notifications/mailer/mailer.service.ts
index a25c80f0d..60e3197e6 100644
--- a/server/src/nest/notifications/mailer/mailer.service.ts
+++ b/server/src/nest/notifications/mailer/mailer.service.ts
@@ -23,13 +23,22 @@ interface SmtpConfig {
  * pressing "Send test email" against a blocked port got a dead "Test email
  * failed" while the socket was still waiting, and the eventual error had nobody
  * left to tell. A relay that needs more than ten seconds to accept a connection
- * or to send its banner is broken either way, so those two are cut hard. The
- * inactivity timeout stays generous (nodemailer's default is ten minutes)
- * because a relay that scans the message can be slow to acknowledge DATA.
+ * or to send its banner is broken either way, so those two are cut hard.
+ *
+ * The inactivity timeout is the one that must not be cut, and it splits by
+ * caller. It only starts counting once the relay has answered its greeting, so
+ * what it bounds is the transfer itself, and a relay that scans the message can
+ * sit on DATA for minutes before it acknowledges. A real send therefore keeps
+ * nodemailer's ten minutes: nobody is waiting on it, and a password-reset mail
+ * that is dropped because the scanner was slow fails where the user cannot see
+ * it. The admin's test send is the exception, because somebody IS waiting: the
+ * client gives that call 40 seconds (CHANNEL_TEST_TIMEOUT), so the verdict has
+ * to arrive inside it.
  */
 const CONNECT_TIMEOUT_MS = 10_000;
 const GREETING_TIMEOUT_MS = 10_000;
-const SOCKET_TIMEOUT_MS = 30_000;
+const SOCKET_TIMEOUT_MS = 600_000;
+const TEST_SOCKET_TIMEOUT_MS = 30_000;
 
 /**
  * Outgoing mail: SMTP config resolution, the password-reset delivery and the
@@ -86,7 +95,7 @@ export class MailerService {
    * The three call sites below each built this inline before the fold; keeping it
    * one method is the only change, and it keeps the freshness property visible.
    */
-  private createTransport(config: SmtpConfig) {
+  private createTransport(config: SmtpConfig, socketTimeoutMs: number = SOCKET_TIMEOUT_MS) {
     const skipTls = readEnv().smtp.skipTlsVerify || this.getAppSetting('smtp_skip_tls_verify') === 'true';
     if (skipTls) this.warnOnceAboutSkippedTls(config);
     return nodemailer.createTransport({
@@ -96,7 +105,7 @@ export class MailerService {
       auth: config.user ? { user: config.user, pass: config.pass } : undefined,
       connectionTimeout: CONNECT_TIMEOUT_MS,
       greetingTimeout: GREETING_TIMEOUT_MS,
-      socketTimeout: SOCKET_TIMEOUT_MS,
+      socketTimeout: socketTimeoutMs,
       // The operator's opt-out for a relay with a self-signed certificate, off by
       // default and reachable only through SMTP_SKIP_TLS_VERIFY or the matching
       // admin setting. It stays because self-hosted installs behind an internal
@@ -233,7 +242,7 @@ export class MailerService {
       return { success: false, error: reason };
     }
     try {
-      await this.createTransport(config).sendMail({
+      await this.createTransport(config, TEST_SOCKET_TIMEOUT_MS).sendMail({
         from: config.from,
         to,
         subject: 'TREK — Test Notification',
diff --git a/server/tests/unit/nest/mailer.service.test.ts b/server/tests/unit/nest/mailer.service.test.ts
index 38016c8d1..55d0707bb 100644
--- a/server/tests/unit/nest/mailer.service.test.ts
+++ b/server/tests/unit/nest/mailer.service.test.ts
@@ -147,13 +147,30 @@ describe('MailerService TLS options', () => {
     expect(sendMail).not.toHaveBeenCalled();
   });
 
-  it('MAILER-007: every SMTP phase is bounded, so a dead relay fails instead of hanging', async () => {
+  it('MAILER-007: connecting and greeting are bounded hard, the transfer is not', async () => {
     configureSmtp();
 
     await newMailer().sendEmail('someone@example.com', 'Subject', 'Body');
 
-    // Nodemailer's own defaults (120s / 30s / 600s) all outlive the client's 8s
-    // API timeout, which is how #2196 produced a failure nobody could read.
+    // Nodemailer's connect and greeting defaults (120s / 30s) outlive the client's
+    // 8s API timeout, which is how #2196 produced a failure nobody could read. The
+    // inactivity timeout keeps its ten minutes on a real send: it bounds the
+    // transfer, a scanning relay can sit on DATA for minutes, and nobody is
+    // waiting on the result.
+    expect(lastTransportOptions()).toMatchObject({
+      connectionTimeout: 10_000,
+      greetingTimeout: 10_000,
+      socketTimeout: 600_000,
+    });
+  });
+
+  it('MAILER-007b: the admin test send bounds the transfer too, because somebody is waiting', async () => {
+    configureSmtp();
+
+    await newMailer().testSmtp('someone@example.com');
+
+    // The client gives this call 40s (CHANNEL_TEST_TIMEOUT), so a relay that
+    // accepts the connection and then goes quiet still has to produce a verdict.
     expect(lastTransportOptions()).toMatchObject({
       connectionTimeout: 10_000,
       greetingTimeout: 10_000,