diff --git a/templates/smtp/server.py b/templates/smtp/server.py
index b5b2232..3f524fe 100644
--- a/templates/smtp/server.py
+++ b/templates/smtp/server.py
@@ -87,9 +87,10 @@ class SMTPProtocol(asyncio.Protocol):
 
     def data_received(self, data):
         self._buf += data
-        while b"\r\n" in self._buf:
-            line, self._buf = self._buf.split(b"\r\n", 1)
-            self._handle_line(line.decode(errors="replace"))
+        while b"\n" in self._buf:
+            line, self._buf = self._buf.split(b"\n", 1)
+            # Strip trailing \r so both CRLF and bare LF work
+            self._handle_line(line.rstrip(b"\r").decode(errors="replace"))
 
     def connection_lost(self, exc):
         _log("disconnect", src=self._peer[0] if self._peer else "?")
@@ -118,7 +119,12 @@ class SMTPProtocol(asyncio.Protocol):
                 self._data_buf.append(line[1:] if line.startswith(".") else line)
             return
 
-        # ── AUTH multi-step (LOGIN mechanism) ─────────────────────────────────
+        # ── AUTH multi-step (LOGIN / PLAIN continuation) ─────────────────────
+        if self._auth_state == "await_plain":
+            user, password = _decode_auth_plain(line)
+            self._finish_auth(user, password)
+            self._auth_state = ""
+            return
         if self._auth_state == "await_user":
             self._auth_user  = base64.b64decode(line + "==").decode(errors="replace")
             self._auth_state = "await_pass"
diff --git a/tests/service_testing/test_smtp.py b/tests/service_testing/test_smtp.py
index 8a6e93a..b4005e3 100644
--- a/tests/service_testing/test_smtp.py
+++ b/tests/service_testing/test_smtp.py
@@ -301,3 +301,78 @@ def test_decode_auth_plain_garbage_no_raise(relay_mod):
     user, pw = relay_mod._decode_auth_plain("!!!notbase64!!!")
     assert isinstance(user, str)
     assert isinstance(pw, str)
+
+
+# ── Bare LF line endings ────────────────────────────────────────────────────
+
+def _send_bare_lf(proto, *lines: str) -> None:
+    """Feed LF-only terminated lines to the protocol (simulates telnet/nc)."""
+    for line in lines:
+        proto.data_received((line + "\n").encode())
+
+
+def test_ehlo_works_with_bare_lf(relay_mod):
+    """Clients sending bare LF (telnet, nc) must get EHLO responses."""
+    proto, _, written = _make_protocol(relay_mod)
+    _send_bare_lf(proto, "EHLO attacker.com")
+    combined = b"".join(written).decode()
+    assert "250" in combined
+    assert "AUTH" in combined
+
+
+def test_full_session_with_bare_lf(relay_mod):
+    """A complete relay session using bare LF line endings."""
+    proto, _, written = _make_protocol(relay_mod)
+    _send_bare_lf(
+        proto,
+        "EHLO attacker.com",
+        "MAIL FROM:<hacker@evil.com>",
+        "RCPT TO:<admin@target.com>",
+        "DATA",
+        "Subject: test",
+        "",
+        "body",
+        ".",
+        "QUIT",
+    )
+    replies = _replies(written)
+    assert any("queued as" in r for r in replies)
+    assert any(r.startswith("221") for r in replies)
+
+
+def test_mixed_line_endings(relay_mod):
+    """A single data_received call containing a mix of CRLF and bare LF."""
+    proto, _, written = _make_protocol(relay_mod)
+    proto.data_received(b"EHLO test.com\r\nMAIL FROM:<a@b.com>\nRCPT TO:<c@d.com>\r\n")
+    replies = _replies(written)
+    assert any("250" in r for r in replies)
+    assert any(r.startswith("250 2.1.0") for r in replies)
+    assert any(r.startswith("250 2.1.5") for r in replies)
+
+
+# ── AUTH PLAIN continuation (no inline credentials) ──────────────────────────
+
+def test_auth_plain_continuation_relay(relay_mod):
+    """AUTH PLAIN without inline creds should prompt then accept on next line."""
+    proto, _, written = _make_protocol(relay_mod)
+    _send(proto, "AUTH PLAIN")
+    replies = _replies(written)
+    assert any(r.startswith("334") for r in replies), "Expected 334 continuation"
+    written.clear()
+    creds = base64.b64encode(b"\x00admin\x00password").decode()
+    _send(proto, creds)
+    replies = _replies(written)
+    assert any(r.startswith("235") for r in replies), "Expected 235 auth success"
+
+
+def test_auth_plain_continuation_harvester(harvester_mod):
+    """AUTH PLAIN continuation in harvester mode should reject with 535."""
+    proto, _, written = _make_protocol(harvester_mod)
+    _send(proto, "AUTH PLAIN")
+    replies = _replies(written)
+    assert any(r.startswith("334") for r in replies)
+    written.clear()
+    creds = base64.b64encode(b"\x00admin\x00password").decode()
+    _send(proto, creds)
+    replies = _replies(written)
+    assert any(r.startswith("535") for r in replies)