crates/common/src/network/legacy.rs

@@ -17,11 +17,16 @@
 //! back on the next restart. Opening puts the object back first and then
 //! spawns, for the same reason in reverse.
 //!
+//! Sign-in is the second lock (LP-6): while the switch is off, a sign-in over
+//! a legacy protocol is refused before any password is looked at, so a
+//! listener that exists by mistake still lets nobody in.
+//!
 //! Nothing here touches the host's firewall, NAT port-forwards or any proxy
 //! (LP-20). The server stops answering; what still routes the port is the
 //! operator's to reconcile.
 
 use crate::{Server, config::server::Listeners, network::TcpAcceptor};
+use directory::Credentials;
 use inbuxa_features::security::{
     listeners,
     protocol_policy::{self, ProtocolPolicy, SavedListener},
@@ -209,3 +214,150 @@ impl Server {
             .collect())
     }
 }
+
+/// A protocol a mail app signs in over, which the switch refuses (LP-6).
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum LegacyProtocol {
+    Imap,
+    Pop3,
+    ManageSieve,
+    /// SMTP AUTH, on any SMTP listener: only mail apps authenticate, so
+    /// inbound delivery is untouched (LP-3).
+    Submission,
+}
+
+impl LegacyProtocol {
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            LegacyProtocol::Imap => "imap",
+            LegacyProtocol::Pop3 => "pop3",
+            LegacyProtocol::ManageSieve => "manageSieve",
+            LegacyProtocol::Submission => "submission",
+        }
+    }
+
+    /// What the mail app is told, at server scope (LP-12, LP-6). Each
+    /// protocol's own framing — IMAP's `[ALERT]`, ManageSieve's quoting —
+    /// is added by its session; POP3 carries `[AUTH]` in the text, since its
+    /// errors have no separate code, and SMTP is the whole reply line.
+    pub fn refusal(&self) -> &'static str {
+        match self {
+            LegacyProtocol::Imap => {
+                "This server allows only INBUXA webmail and JMAP apps. This mail app can't sign in."
+            }
+            LegacyProtocol::Pop3 => {
+                "[AUTH] This server allows only INBUXA webmail and JMAP apps. This mail app can't sign in."
+            }
+            LegacyProtocol::ManageSieve => "This server allows only INBUXA webmail and JMAP apps.",
+            LegacyProtocol::Submission => {
+                "535 5.7.0 This server allows only INBUXA webmail and JMAP apps. This mail app can't send.\r\n"
+            }
+        }
+    }
+
+    /// The refusal as an error: `auth.legacy-protocol-refused`, not
+    /// `auth.failed`, so it never counts against the account or feeds the
+    /// auto-ban (LP-11). It names the protocol and the domain, never the
+    /// account; the session it is raised in adds the remote IP.
+    pub fn refused(&self, credentials: &Credentials) -> trc::Error {
+        trc::AuthEvent::LegacyProtocolRefused
+            .into_err()
+            .details(self.refusal())
+            .ctx(trc::Key::Source, self.as_str())
+            .ctx(trc::Key::Policy, "server")
+            .ctx_opt(trc::Key::Domain, domain_of(credentials))
+    }
+}
+
+/// The domain a sign-in is for, from the name it gives, if it gives one.
+fn domain_of(credentials: &Credentials) -> Option<String> {
+    let username = match credentials {
+        Credentials::Basic { username, .. } => Some(username.as_str()),
+        Credentials::Bearer { username, .. } => username.as_deref(),
+    }?;
+    username
+        .rsplit_once('@')
+        .map(|(_, domain)| domain.trim().to_lowercase())
+        .filter(|domain| !domain.is_empty())
+}
+
+impl Server {
+    /// Refuses a sign-in over a legacy protocol while the server-wide switch
+    /// is off (LP-6). Called before the credentials are checked, so the
+    /// answer is the same for a right password, a wrong one and an account
+    /// that doesn't exist (LP-11).
+    ///
+    /// Read from the store on each sign-in rather than cached, so every node
+    /// of a cluster answers the same the moment the switch turns.
+    pub async fn refuse_legacy_sign_in(
+        &self,
+        protocol: LegacyProtocol,
+        credentials: &Credentials,
+    ) -> trc::Result<()> {
+        if self.protocol_policy().await?.legacy_protocols.is_disabled() {
+            Err(protocol.refused(credentials))
+        } else {
+            Ok(())
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn basic(username: &str) -> Credentials {
+        Credentials::Basic {
+            username: username.to_string(),
+            secret: "wrong or right, it is never read".to_string(),
+            mfa_token: None,
+        }
+    }
+
+    #[test]
+    fn refusals_read_as_the_spec_writes_them() {
+        // LP-12, with "Your organization" read as "This server" (LP-6).
+        assert_eq!(
+            LegacyProtocol::Imap.refusal(),
+            "This server allows only INBUXA webmail and JMAP apps. This mail app can't sign in."
+        );
+        assert!(
+            LegacyProtocol::Pop3
+                .refusal()
+                .starts_with("[AUTH] This server allows")
+        );
+        assert_eq!(
+            LegacyProtocol::ManageSieve.refusal(),
+            "This server allows only INBUXA webmail and JMAP apps."
+        );
+        assert_eq!(
+            LegacyProtocol::Submission.refusal(),
+            "535 5.7.0 This server allows only INBUXA webmail and JMAP apps. This mail app can't send.\r\n"
+        );
+    }
+
+    #[test]
+    fn a_refusal_is_not_a_failed_sign_in() {
+        let err = LegacyProtocol::Imap.refused(&basic("[email protected]"));
+        assert!(err.matches(trc::EventType::Auth(trc::AuthEvent::LegacyProtocolRefused)));
+        assert!(!err.matches(trc::EventType::Auth(trc::AuthEvent::Failed)));
+        // The session stays open: the mail app is told, not thrown off.
+        assert!(!err.must_disconnect());
+        assert!(err.should_write_err());
+        assert_eq!(err.value_as_str(trc::Key::Domain), Some("example.org"));
+        assert_eq!(err.value_as_str(trc::Key::Source), Some("imap"));
+        assert_eq!(err.value_as_str(trc::Key::AccountName), None);
+    }
+
+    #[test]
+    fn the_domain_comes_from_the_name_given() {
+        assert_eq!(domain_of(&basic("[email protected]")), Some("b.test".to_string()));
+        assert_eq!(domain_of(&basic("no-domain")), None);
+        assert_eq!(domain_of(&basic("trailing@")), None);
+        let bearer = Credentials::Bearer {
+            username: None,
+            token: "t".to_string(),
+        };
+        assert_eq!(domain_of(&bearer), None);
+    }
+}

crates/imap/src/op/authenticate.rs

@@ -2,12 +2,14 @@
  * SPDX-FileCopyrightText: 2020 Stalwart Labs LLC <[email protected]>
  *
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
+ *
+ * Modified by Coffey Labs in 2026 for INBUXA.
  */
 
 use crate::core::{Session, SessionData, State};
 use common::{
     auth::AuthRequest,
-    network::{SessionStream, limiter::LimiterResult},
+    network::{SessionStream, legacy::LegacyProtocol, limiter::LimiterResult},
 };
 use directory::Credentials;
 use imap_proto::{
@@ -67,6 +69,12 @@ impl<T: SessionStream> Session<T> {
     }
 
     pub async fn authenticate(&mut self, credentials: Credentials, tag: String) -> trc::Result<()> {
+        // inbuxa: legacy-protocols LP-6, before the password is looked at
+        self.server
+            .refuse_legacy_sign_in(LegacyProtocol::Imap, &credentials)
+            .await
+            .map_err(|err| err.code(ResponseCode::Alert).id(tag.clone()))?;
+
         // Authenticate
         let access_token = self
             .server

crates/managesieve/src/op/authenticate.rs

@@ -2,12 +2,14 @@
  * SPDX-FileCopyrightText: 2020 Stalwart Labs LLC <[email protected]>
  *
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
+ *
+ * Modified by Coffey Labs in 2026 for INBUXA.
  */
 
 use crate::core::{Command, Session, State, StatusResponse};
 use common::{
     auth::AuthRequest,
-    network::{SessionStream, limiter::LimiterResult},
+    network::{SessionStream, legacy::LegacyProtocol, limiter::LimiterResult},
 };
 use directory::Credentials;
 use imap_proto::{
@@ -65,6 +67,11 @@ impl<T: SessionStream> Session<T> {
             }
         };
 
+        // inbuxa: legacy-protocols LP-6, before the password is looked at
+        self.server
+            .refuse_legacy_sign_in(LegacyProtocol::ManageSieve, &credentials)
+            .await?;
+
         // Authenticate
         let access_token = self
             .server

crates/pop3/src/op/authenticate.rs

@@ -2,6 +2,8 @@
  * SPDX-FileCopyrightText: 2020 Stalwart Labs LLC <[email protected]>
  *
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
+ *
+ * Modified by Coffey Labs in 2026 for INBUXA.
  */
 
 use crate::{
@@ -10,7 +12,7 @@ use crate::{
 };
 use common::{
     auth::AuthRequest,
-    network::{SessionStream, limiter::LimiterResult},
+    network::{SessionStream, legacy::LegacyProtocol, limiter::LimiterResult},
 };
 use directory::Credentials;
 use mail_parser::decoders::base64::base64_decode;
@@ -61,6 +63,11 @@ impl<T: SessionStream> Session<T> {
     }
 
     pub async fn handle_auth(&mut self, credentials: Credentials) -> trc::Result<()> {
+        // inbuxa: legacy-protocols LP-6, before the password is looked at
+        self.server
+            .refuse_legacy_sign_in(LegacyProtocol::Pop3, &credentials)
+            .await?;
+
         // Authenticate
         let access_token = self
             .server

crates/smtp/src/inbound/auth.rs

@@ -2,10 +2,15 @@
  * SPDX-FileCopyrightText: 2020 Stalwart Labs LLC <[email protected]>
  *
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
+ *
+ * Modified by Coffey Labs in 2026 for INBUXA.
  */
 
 use crate::core::Session;
-use common::{auth::AuthRequest, network::SessionStream};
+use common::{
+    auth::AuthRequest,
+    network::{SessionStream, legacy::LegacyProtocol},
+};
 use directory::Credentials;
 use mail_parser::decoders::base64::base64_decode;
 use registry::schema::enums::Permission;
@@ -108,6 +113,26 @@ impl<T: SessionStream> Session<T> {
     }
 
     pub async fn authenticate(&mut self, credentials: Credentials) -> Result<bool, ()> {
+        // inbuxa: legacy-protocols LP-6. Refused before the password is looked
+        // at, and not counted as an authentication error (LP-11). Only mail
+        // apps authenticate, so this never touches inbound delivery (LP-3).
+        if let Err(err) = self
+            .server
+            .refuse_legacy_sign_in(LegacyProtocol::Submission, &credentials)
+            .await
+        {
+            let refused = err.matches(trc::EventType::Auth(AuthEvent::LegacyProtocolRefused));
+            trc::error!(err.span_id(self.data.session_id));
+            if refused {
+                self.write(LegacyProtocol::Submission.refusal().as_bytes())
+                    .await?;
+            } else {
+                self.write(b"454 4.7.0 Temporary authentication failure\r\n")
+                    .await?;
+            }
+            return Ok(false);
+        }
+
         // Authenticate
         let result = self
             .server

crates/trc/src/event/enums.rs

@@ -8,8 +8,9 @@
 
 // This file is auto-generated. Do not edit directly.
 
-// inbuxa: 637 to 641 are the fork's SCIM events (SCIM-54)
-pub const TOTAL_EVENT_COUNT: usize = 642;
+// inbuxa: 637 to 641 are the fork's SCIM events (SCIM-54); 642 is
+// auth.legacy-protocol-refused (legacy-protocols LP-6)
+pub const TOTAL_EVENT_COUNT: usize = 643;
 pub const TOTAL_METRIC_COUNT: usize = 369;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
@@ -116,6 +117,8 @@ pub enum AuthEvent {
     Error = 34,
     Warning = 595,
     CredentialExpired = 276,
+    // inbuxa: legacy-protocols LP-6
+    LegacyProtocolRefused = 642,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]

crates/trc/src/event/enums_impl.rs

@@ -56,6 +56,8 @@ impl EventType {
             b"auth.mfa-required" => EventType::Auth(AuthEvent::MfaRequired),
             b"auth.too-many-attempts" => EventType::Auth(AuthEvent::TooManyAttempts),
             b"auth.client-registration" => EventType::Auth(AuthEvent::ClientRegistration),
+            // inbuxa: legacy-protocols LP-6
+            b"auth.legacy-protocol-refused" => EventType::Auth(AuthEvent::LegacyProtocolRefused),
             b"auth.error" => EventType::Auth(AuthEvent::Error),
             b"auth.warning" => EventType::Auth(AuthEvent::Warning),
             b"auth.credential-expired" => EventType::Auth(AuthEvent::CredentialExpired),
@@ -705,6 +707,8 @@ impl EventType {
             EventType::Auth(AuthEvent::MfaRequired) => "auth.mfa-required",
             EventType::Auth(AuthEvent::TooManyAttempts) => "auth.too-many-attempts",
             EventType::Auth(AuthEvent::ClientRegistration) => "auth.client-registration",
+            // inbuxa: legacy-protocols LP-6
+            EventType::Auth(AuthEvent::LegacyProtocolRefused) => "auth.legacy-protocol-refused",
             EventType::Auth(AuthEvent::Error) => "auth.error",
             EventType::Auth(AuthEvent::Warning) => "auth.warning",
             EventType::Auth(AuthEvent::CredentialExpired) => "auth.credential-expired",
@@ -1489,6 +1493,8 @@ impl EventType {
             EventType::Auth(AuthEvent::MfaRequired) => 36,
             EventType::Auth(AuthEvent::TooManyAttempts) => 38,
             EventType::Auth(AuthEvent::ClientRegistration) => 555,
+            // inbuxa: legacy-protocols LP-6
+            EventType::Auth(AuthEvent::LegacyProtocolRefused) => 642,
             EventType::Auth(AuthEvent::Error) => 34,
             EventType::Auth(AuthEvent::Warning) => 595,
             EventType::Auth(AuthEvent::CredentialExpired) => 276,
@@ -2137,6 +2143,8 @@ impl EventType {
             36 => Some(EventType::Auth(AuthEvent::MfaRequired)),
             38 => Some(EventType::Auth(AuthEvent::TooManyAttempts)),
             555 => Some(EventType::Auth(AuthEvent::ClientRegistration)),
+            // inbuxa: legacy-protocols LP-6
+            642 => Some(EventType::Auth(AuthEvent::LegacyProtocolRefused)),
             34 => Some(EventType::Auth(AuthEvent::Error)),
             595 => Some(EventType::Auth(AuthEvent::Warning)),
             276 => Some(EventType::Auth(AuthEvent::CredentialExpired)),
@@ -2848,6 +2856,8 @@ impl EventType {
             EventType::Acme(AcmeEvent::TlsAlpnReceived) => Level::Info,
             EventType::Auth(AuthEvent::Success) => Level::Info,
             EventType::Auth(AuthEvent::ClientRegistration) => Level::Info,
+            // inbuxa: legacy-protocols LP-6
+            EventType::Auth(AuthEvent::LegacyProtocolRefused) => Level::Info,
             EventType::Calendar(CalendarEvent::AlarmSent) => Level::Info,
             EventType::Calendar(CalendarEvent::ItipMessageSent) => Level::Info,
             EventType::Calendar(CalendarEvent::ItipMessageReceived) => Level::Info,
@@ -3187,6 +3197,8 @@ impl EventType {
             EventType::Auth(AuthEvent::MfaRequired) => "Missing MFA token for authentication",
             EventType::Auth(AuthEvent::TooManyAttempts) => "Too many authentication attempts",
             EventType::Auth(AuthEvent::ClientRegistration) => "OAuth Client registration",
+            // inbuxa: legacy-protocols LP-6
+            EventType::Auth(AuthEvent::LegacyProtocolRefused) => "Legacy mail protocol sign-in refused",
             EventType::Auth(AuthEvent::Error) => "Authentication error",
             EventType::Auth(AuthEvent::Warning) => "Authentication warning",
             EventType::Auth(AuthEvent::CredentialExpired) => "Credential expired",
@@ -3951,6 +3963,8 @@ impl EventType {
             }
             EventType::Auth(AuthEvent::TooManyAttempts) => "Too many authentication attempts",
             EventType::Auth(AuthEvent::ClientRegistration) => "Authentication error",
+            // inbuxa: legacy-protocols LP-6
+            EventType::Auth(AuthEvent::LegacyProtocolRefused) => "This server allows only INBUXA webmail and JMAP apps",
             EventType::Auth(AuthEvent::Error) => "Authentication error",
             EventType::Auth(AuthEvent::CredentialExpired) => "Credential expired",
             EventType::Imap(ImapEvent::ConnectionStart) => "IMAP error",
@@ -4259,6 +4273,8 @@ impl EventType {
             EventType::Auth(AuthEvent::MfaRequired),
             EventType::Auth(AuthEvent::TooManyAttempts),
             EventType::Auth(AuthEvent::ClientRegistration),
+            // inbuxa: legacy-protocols LP-6
+            EventType::Auth(AuthEvent::LegacyProtocolRefused),
             EventType::Auth(AuthEvent::Error),
             EventType::Auth(AuthEvent::Warning),
             EventType::Auth(AuthEvent::CredentialExpired),

resources/schema/schema.json.sha256

@@ -1 +1 @@
--DHPbeChvvEHbLbAO3wDU6KCP8HrzaWZHfkka30YoIU
+C32Zc43ANGr52j0cZkTq3IEPrGtbFUX0d2-R91noCho

tests/e2e/legacy_protocols.py

@@ -12,6 +12,12 @@ This is the part unit tests cannot reach: whether a socket actually closes on
 a running server (LP-2), and whether a listener put back actually binds again
 (LP-5). Acceptance tests 15, 17 and 18.
 
+It also checks the second lock (LP-6): while the switch is off, sign-in over
+submission -- locked open -- and over an IMAP listener that exists by mistake
+is refused with the spec's words, with the right password and with a wrong
+one, and refusals never add up to a disconnect (LP-11). And that a normal
+IMAP sign-in works with the switch on, before and after.
+
 Passwords are generated into files under target/e2e and never printed.
 Everything is removed afterwards unless KEEP=1.
 """
@@ -25,8 +31,12 @@ HTTP = "http://127.0.0.1:18080"
 # makes the host side accept connections whether or not anything is listening
 # inside the container, so a bare connect proves nothing: each port has to be
 # made to speak.
-PORTS = {"imap": 18993, "pop3": 18995, "submissions": 18465, "smtp": 18025}
-TLS_PORTS = {18993, 18995, 18465}
+PORTS = {"imap": 18993, "pop3": 18995, "submissions": 18465, "smtp": 18025, "mistake": 18994}
+TLS_PORTS = {18993, 18995, 18465, 18994}
+IMAP_REFUSAL = ("NO [ALERT] This server allows only INBUXA webmail and JMAP apps. "
+                "This mail app can't sign in.")
+SMTP_REFUSAL = ("535 5.7.0 This server allows only INBUXA webmail and JMAP apps. "
+                "This mail app can't send.")
 INBUXA = "urn:inbuxa:jmap"
 failures = []
 
@@ -60,7 +70,8 @@ def start(env_file=None):
             "-p", f"127.0.0.1:{PORTS['submissions']}:465",
             "-p", f"127.0.0.1:{PORTS['imap']}:993",
             "-p", f"127.0.0.1:{PORTS['pop3']}:995",
-            "-p", f"127.0.0.1:{PORTS['smtp']}:25"]
+            "-p", f"127.0.0.1:{PORTS['smtp']}:25",
+            "-p", f"127.0.0.1:{PORTS['mistake']}:1993"]
     if env_file:
         args += ["--env-file", env_file]
     args += ["stalwartlabs/stalwart:v0.16.22", "--config", "/etc/inbuxa/config.json"]
@@ -122,6 +133,64 @@ def accepts(port, timeout=5):
         return False
 
 
+def tls(port, timeout=10):
+    ctx = ssl.create_default_context()
+    ctx.check_hostname = False
+    ctx.verify_mode = ssl.CERT_NONE
+    return ctx.wrap_socket(socket.create_connection(("127.0.0.1", port), timeout=timeout))
+
+
+def lines(sock):
+    """Yields reply lines, CRLF stripped."""
+    buf = b""
+    while True:
+        while b"\r\n" not in buf:
+            chunk = sock.recv(4096)
+            if not chunk:
+                return
+            buf += chunk
+        line, buf = buf.split(b"\r\n", 1)
+        yield line.decode(errors="replace")
+
+
+def imap_login(port, user, password):
+    """The tagged reply to LOGIN, over implicit TLS."""
+    with tls(port) as sock:
+        read = lines(sock)
+        next(read)  # greeting
+        quote = lambda v: '"' + v.replace("\\", "\\\\").replace('"', '\\"') + '"'
+        sock.sendall(f"a1 LOGIN {quote(user)} {quote(password)}\r\n".encode())
+        for line in read:
+            if line.startswith("a1 "):
+                return line[3:]
+    return ""
+
+
+def smtp_auths(port, user, passwords):
+    """The reply to AUTH PLAIN for each password in turn, on one connection.
+    A reply of "" means the server hung up."""
+    # Every connection reaches the server from Docker's gateway, one IP, and
+    # the stock inbound throttle takes five a second from it. The port checks
+    # just before can use those up, so wait the second out.
+    time.sleep(1.1)
+    replies = []
+    with tls(port) as sock:
+        read = lines(sock)
+        next(read)  # greeting
+        sock.sendall(b"EHLO e2e.test\r\n")
+        for line in read:
+            if line[3:4] == " ":
+                break
+        for password in passwords:
+            token = base64.b64encode(f"\0{user}\0{password}".encode()).decode()
+            try:
+                sock.sendall(f"AUTH PLAIN {token}\r\n".encode())
+                replies.append(next(read, ""))
+            except OSError:
+                replies.append("")
+    return replies
+
+
 def settle(port, want, tries=30):
     """Wait for a port to reach the wanted state, so the check is not a race."""
     for _ in range(tries):
@@ -176,6 +245,12 @@ def main():
     check(accepts(PORTS["submissions"]), "submission accepts before the switch")
     check(accepts(PORTS["smtp"]), "inbound SMTP accepts before the switch")
 
+    # A normal sign-in works with the switch on -- the control for LP-6.
+    check(imap_login(PORTS["imap"], admin, admin_pw).startswith("OK"),
+          "IMAP sign-in works with the switch on")
+    check(smtp_auths(PORTS["submissions"], admin, [admin_pw])[0].startswith("235"),
+          "submission sign-in works with the switch on")
+
     # What the screen reads: the locked set and what would close (LP-16, LP-21).
     got = one(admin, admin_pw, "inbuxa:ProtocolPolicy/get", policy_get)
     if got[0] != "inbuxa:ProtocolPolicy/get":
@@ -212,12 +287,40 @@ def main():
     print("     savedListeners:", sorted(saved))
     check(saved, "the closed listeners were saved (LP-1)")
 
+    # The second lock (LP-6). Submission stays open, being locked, so sign-in
+    # over it is refused instead -- right password or wrong, the same words,
+    # and never enough of them to be thrown off (LP-11, test 2, test 18).
+    replies = smtp_auths(PORTS["submissions"], admin, [admin_pw] + ["wrong"] * 6)
+    check(replies[0] == SMTP_REFUSAL, "submission refuses the right password (LP-6)")
+    check(all(r == SMTP_REFUSAL for r in replies[1:]),
+          "submission refuses wrong passwords the same way, and doesn't hang up (LP-11)")
+    if not all(r == SMTP_REFUSAL for r in replies):
+        print("     replies:", replies)
+
+    # An IMAP listener that exists by mistake: created while the switch is off
+    # (LP-4 will refuse this later), and live after the restart below.
+    res = one(admin, admin_pw, "x:NetworkListener/set", {"create": {"m": {
+        "name": "imap-mistake", "protocol": "imap", "bind": {"0.0.0.0:1993": True},
+        "tlsImplicit": True}}})
+    mistake = (res[1].get("created") or {}).get("m", {}).get("id")
+    check(mistake is not None, "an IMAP listener can still be created by mistake")
+
     # A restart must not reopen them: the objects are gone, not just the sockets.
     stop()
     start()
     check(settle(PORTS["imap"], False), "IMAP still closed after a restart")
     check(accepts(PORTS["smtp"]), "inbound SMTP still accepts after a restart")
 
+    if mistake:
+        check(settle(PORTS["mistake"], True), "the mistaken IMAP listener is up")
+        check(imap_login(PORTS["mistake"], admin, admin_pw) == IMAP_REFUSAL,
+              "the mistaken listener refuses the right password (LP-6)")
+        check(imap_login(PORTS["mistake"], admin, "wrong") == IMAP_REFUSAL,
+              "and a wrong one, the same way (LP-11)")
+        check(imap_login(PORTS["mistake"], "[email protected]", "x") == IMAP_REFUSAL,
+              "and an account that doesn't exist (LP-11)")
+        one(admin, admin_pw, "x:NetworkListener/set", {"destroy": [mistake]})
+
     # Turn it back on: the listeners come back and bind again (LP-5).
     res = one(admin, admin_pw, "inbuxa:ProtocolPolicy/set",
               policy_set({"legacyProtocols": "enabled"}))
@@ -231,6 +334,12 @@ def main():
     check(policy["legacyProtocols"] == "enabled", "switch reads back enabled")
     check(not policy["savedListeners"], "savedListeners is empty again (LP-5)")
 
+    # And sign-in works again, with no restart.
+    check(imap_login(PORTS["imap"], admin, admin_pw).startswith("OK"),
+          "IMAP sign-in works again once the switch is back on")
+    check(smtp_auths(PORTS["submissions"], admin, [admin_pw])[0].startswith("235"),
+          "submission sign-in works again once the switch is back on")
+
     print()
     if failures:
         print(f"{len(failures)} FAILED:")