dovecot: increase number of simultaneous connections handled by imap-login

Otherwise deltachat core CI running fails with "Connection queue full"
error on IMAP connections.

.github/workflows/ci.yaml

@@ -5,14 +5,27 @@ on:
   push:
 
 jobs:
-  lint:
-    name: Lint
+  tox:
+    name: chatmail tests
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - name: Lint chatmaild
+      - name: run chatmaild tests 
         working-directory: chatmaild
         run: pipx run tox
-      - name: Lint deploy-chatmail
+      - name: run deploy-chatmail offline tests 
         working-directory: deploy-chatmail
         run: pipx run tox
+      - name: run deploy-chatmail offline tests 
+        working-directory: deploy-chatmail
+        run: pipx run tox
+
+  scripts:
+    name: chatmail script invocations 
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: run init.sh 
+        run: ./scripts/init.sh 
+      - name: run test.sh 
+        run: ./scripts/test.sh 

.gitignore

@@ -159,3 +159,5 @@ cython_debug/
 #  and can be added to the global gitignore or merged into this file.  For a more nuclear
 #  option (not recommended) you can uncomment the following to ignore the entire idea folder.
 #.idea/
+
+chatmail.zone

README.md

@@ -10,14 +10,17 @@ comprised of a minimal setup of the battle-tested
 
     scripts/init.sh 
 
-2. set environment variable to the chatmail domain you want to setup:
+2. setup a domain with `A` and `AAAA` records for your chatmail server
+
+3. set environment variable to the chatmail domain you want to setup:
 
     export CHATMAIL_DOMAIN=c1.testrun.org   # replace with your host
 
-3. run the deploy of the chat mail instance: 
+4. run the deploy of the chat mail instance: 
 
     scripts/deploy.sh 
 
+5. run `scripts/generate-dns-zone.sh` and create the generated DNS records at your DNS provider
 
 ## Running tests and benchmarks (offline and online) 
 

chatmaild/pyproject.toml

@@ -20,7 +20,7 @@ addopts = "-v -ra --strict-markers"
 legacy_tox_ini = """
 [tox]
 isolated_build = true
-envlist = lint
+envlist = lint,py
 
 [testenv:lint]
 skipdist = True
@@ -31,4 +31,10 @@ deps =
 commands =
   black --quiet --check --diff src/
   ruff src/
+
+[testenv]
+passenv = CHATMAIL_DOMAIN
+deps = pytest 
+       pdbpp 
+commands = pytest -v -rsXx {posargs: ../tests/chatmaild}
 """

chatmaild/src/chatmaild/dictproxy.py

@@ -21,68 +21,81 @@ def encrypt_password(password: str):
     return "{SHA512-CRYPT}" + passhash
 
 
-class DictProxy:
-    def __init__(self, db, mail_domain):
-        self.db = db
-        self.mail_domain = mail_domain
+def check_password(password) -> bool:
+    """Check password policy"""
+    if len(password) < 10:
+        return False
+    return True
 
-    def create_user(self, user, password):
-        if os.path.exists(NOCREATE_FILE):
-            logging.warning(f"Didn't create account: {NOCREATE_FILE} exists.")
+
+def create_user(db, user, encrypted_password):
+    if os.path.exists(NOCREATE_FILE):
+        logging.warning(
+            f"Didn't create account: {NOCREATE_FILE} exists. Delete the file to enable account creation."
+        )
+        return
+    with db.write_transaction() as conn:
+        conn.create_user(user, encrypted_password)
+    return dict(
+        home=f"/home/vmail/{user}",
+        uid="vmail",
+        gid="vmail",
+        password=encrypted_password,
+    )
+
+
+def get_user_data(db, user):
+    with db.read_connection() as conn:
+        result = conn.get_user(user)
+    if result:
+        result["uid"] = "vmail"
+        result["gid"] = "vmail"
+    return result
+
+
+def lookup_userdb(db, user):
+    return get_user_data(db, user)
+
+
+def lookup_passdb(db, user, password):
+    userdata = get_user_data(db, user)
+    if not userdata:
+        if not check_password(password):
+            logging.warning("Attempt to create an account with a weak password.")
             return
-        with self.db.write_transaction() as conn:
-            conn.create_user(user, password)
-        return dict(home=f"/home/vmail/{user}", uid="vmail", gid="vmail", password=password)
-
-    def get_user_data(self, user):
-        with self.db.read_connection() as conn:
-            result = conn.get_user(user)
-        if result:
-            result["uid"] = "vmail"
-            result["gid"] = "vmail"
-        return result
+        return create_user(db, user, encrypt_password(password))
+    userdata["password"] = userdata["password"].strip()
+    return userdata
 
 
-    def lookup_userdb(self, user):
-        return self.get_user_data(user)
-
-
-    def lookup_passdb(self, user, password):
-        userdata = self.get_user_data(user)
-        if not userdata:
-            return self.create_user(user, encrypt_password(password))
-        userdata["password"] = userdata["password"].strip()
-        return userdata
-
-
-    def handle_dovecot_request(self, msg):
-        print(f"received msg: {msg!r}", file=sys.stderr)
-        short_command = msg[0]
-        if short_command == "L":  # LOOKUP
-            parts = msg[1:].split("\t")
-            keyname, user = parts[:2]
-            namespace, type, *args = keyname.split("/")
-            reply_command = "F"
-            res = ""
-            if namespace == "shared":
-                if type == "userdb":
-                    if user.endswith(f"@{self.mail_domain}"):
-                        res = lookup_userdb(db, user)
-                    if res:
-                        reply_command = "O"
-                    else:
-                        reply_command = "N"
-                elif type == "passdb":
-                    if user.endswith(f"@{self.mail_domain}"):
-                        res = lookup_passdb(db, user, password=args[0])
-                    if res:
-                        reply_command = "O"
-                    else:
-                        reply_command = "N"
-            print(f"res: {res!r}", file=sys.stderr)
-            json_res = json.dumps(res) if res else ""
-            return f"{reply_command}{json_res}\n"
-        return None
+def handle_dovecot_request(msg, db, mail_domain):
+    print(f"received msg: {msg!r}", file=sys.stderr)
+    short_command = msg[0]
+    if short_command == "L":  # LOOKUP
+        parts = msg[1:].split("\t")
+        keyname, user = parts[:2]
+        namespace, type, *args = keyname.split("/")
+        reply_command = "F"
+        res = ""
+        if namespace == "shared":
+            if type == "userdb":
+                if user.endswith(f"@{mail_domain}"):
+                    res = lookup_userdb(db, user)
+                if res:
+                    reply_command = "O"
+                else:
+                    reply_command = "N"
+            elif type == "passdb":
+                if user.endswith(f"@{mail_domain}"):
+                    res = lookup_passdb(db, user, password=args[0])
+                if res:
+                    reply_command = "O"
+                else:
+                    reply_command = "N"
+        print(f"res: {res!r}", file=sys.stderr)
+        json_res = json.dumps(res) if res else ""
+        return f"{reply_command}{json_res}\n"
+    return None
 
 
 class ThreadedUnixStreamServer(ThreadingMixIn, UnixStreamServer):
@@ -92,18 +105,17 @@ class ThreadedUnixStreamServer(ThreadingMixIn, UnixStreamServer):
 def main():
     socket = sys.argv[1]
     passwd_entry = pwd.getpwnam(sys.argv[2])
+    db = Database(sys.argv[3])
     with open("/etc/mailname", "r") as fp:
         mail_domain = fp.read().strip()
 
-    db = Database(sys.argv[3])
-    dictproxy = DictProxy(db, mail_domain)
     class Handler(StreamRequestHandler):
         def handle(self):
             while True:
                 msg = self.rfile.readline().strip().decode()
                 if not msg:
                     break
-                res = dictproxy.handle_dovecot_request(msg)
+                res = handle_dovecot_request(msg, db, mail_domain)
                 if res:
                     print(f"sending result: {res!r}", file=sys.stderr)
                     self.wfile.write(res.encode("ascii"))

chatmaild/src/chatmaild/filtermail.py

@@ -34,6 +34,34 @@ def check_encrypted(message):
     return True
 
 
+def check_mdn(message, envelope):
+    if len(envelope.rcpt_tos) != 1:
+        return False
+
+    for name in ["auto-submitted", "chat-version"]:
+        if not message.get(name):
+            return False
+
+    if message.get_content_type() != "multipart/report":
+        return False
+
+    body = message.get_body()
+    if body.get_content_type() != "text/plain":
+        return False
+
+    if list(body.iter_attachments()) or list(body.iter_parts()):
+        return False
+
+    # even with all mime-structural checks an attacker
+    # could try to abuse the subject or body to contain links or other
+    # annoyance -- we skip on checking subject/body for now as Delta Chat
+    # should evolve to create E2E-encrypted read receipts anyway.
+    # and then MDNs are just encrypted mail and can pass the border
+    # to other instances.
+
+    return True
+
+
 class SMTPController(Controller):
     def factory(self):
         return SMTP(self.handler, **self.SMTP_kwargs)
@@ -82,6 +110,9 @@ def check_DATA(envelope):
     if envelope.mail_from.lower() != from_addr.lower():
         return f"500 Invalid FROM <{from_addr!r}> for <{envelope.mail_from!r}>"
 
+    if not mail_encrypted and check_mdn(message, envelope):
+        return
+
     envelope_from_domain = from_addr.split("@").pop()
     for recipient in envelope.rcpt_tos:
         if envelope.mail_from == recipient:

deploy-chatmail/src/deploy_chatmail/__init__.py

@@ -4,8 +4,8 @@ Chat Mail pyinfra deploy.
 import importlib.resources
 from pathlib import Path
 
-from pyinfra import host, logger
-from pyinfra.operations import apt, files, server, systemd, python
+from pyinfra import host
+from pyinfra.operations import apt, files, server, systemd
 from pyinfra.facts.files import File
 from .acmetool import deploy_acmetool
 
@@ -70,6 +70,36 @@ def _configure_opendkim(domain: str, dkim_selector: str) -> bool:
         mode="644",
         config={"domain_name": domain, "opendkim_selector": dkim_selector},
     )
+    need_restart |= main_config.changed
+
+    files.directory(
+        name="Add opendkim directory to /etc",
+        path="/etc/opendkim",
+        user="opendkim",
+        group="opendkim",
+        mode="750",
+        present=True,
+    )
+
+    keytable = files.template(
+        src=importlib.resources.files(__package__).joinpath("opendkim/KeyTable"),
+        dest="/etc/dkimkeys/KeyTable",
+        user="opendkim",
+        group="opendkim",
+        mode="644",
+        config={"domain_name": domain, "opendkim_selector": dkim_selector},
+    )
+    need_restart |= keytable.changed
+
+    signing_table = files.template(
+        src=importlib.resources.files(__package__).joinpath("opendkim/SigningTable"),
+        dest="/etc/dkimkeys/SigningTable",
+        user="opendkim",
+        group="opendkim",
+        mode="644",
+        config={"domain_name": domain, "opendkim_selector": dkim_selector},
+    )
+    need_restart |= signing_table.changed
 
     files.directory(
         name="Add opendkim socket directory to /var/spool/postfix",
@@ -90,8 +120,6 @@ def _configure_opendkim(domain: str, dkim_selector: str) -> bool:
             _sudo_user="opendkim",
         )
 
-    need_restart |= main_config.changed
-
     return need_restart
 
 
@@ -292,14 +320,3 @@ def deploy_chatmail(mail_domain: str, mail_server: str, dkim_selector: str) -> N
         enabled=True,
         restarted=journald_conf,
     )
-
-    def callback():
-        result = server.shell(
-            commands=[
-                f"""sed 's/\tIN/ 600 IN/;s/\t(//;s/\"$//;s/^\t  \"//g; s/ ).*//' """
-                f"""/etc/dkimkeys/{dkim_selector}.txt | tr --delete '\n'"""
-            ]
-        )
-        logger.info(f"Add this TXT entry into DNS zone: {result.stdout}")
-
-    python.call(name="Print TXT entry for DKIM", function=callback)

deploy-chatmail/src/deploy_chatmail/deploy.py

@@ -6,7 +6,7 @@ from deploy_chatmail import deploy_chatmail
 def main():
     mail_domain = os.getenv("CHATMAIL_DOMAIN")
     mail_server = os.getenv("CHATMAIL_SERVER", mail_domain)
-    dkim_selector = os.getenv("CHATMAIL_DKIM_SELECTOR", "2023")
+    dkim_selector = os.getenv("CHATMAIL_DKIM_SELECTOR", "dkim")
 
     assert mail_domain
     assert mail_server

deploy-chatmail/src/deploy_chatmail/dovecot/dovecot.conf.j2

@@ -118,6 +118,24 @@ service auth-worker {
   user = vmail
 }
 
+service imap-login {
+    # High-security mode.
+    # Each process serves a single connection and exits afterwards.
+    # This is the default, but we set it explicitly to be sure.
+    # See <https://doc.dovecot.org/admin_manual/login_processes/#high-security-mode> for details.
+    service_count = 1
+
+    # Inrease the number of simultaneous connections.
+    #
+    # As of Dovecot 2.3.19.1 the default is 100 processes.
+    # Combined with `service_count = 1` it means only 100 connections
+    # can be handled simultaneously.
+    process_limit = 10000
+
+    # Avoid startup latency for new connections.
+    process_min_avail = 10
+}
+
 ssl = required
 ssl_cert = </var/lib/acme/live/{{ config.hostname }}/fullchain
 ssl_key = </var/lib/acme/live/{{ config.hostname }}/privkey

deploy-chatmail/src/deploy_chatmail/opendkim/KeyTable

@@ -0,0 +1 @@
+dkim._domainkey.{{ config.domain_name }} {{ config.domain_name }}:{{ config.opendkim_selector }}:/etc/dkimkeys/dkim.private

deploy-chatmail/src/deploy_chatmail/opendkim/SigningTable

@@ -0,0 +1 @@
+*@{{ config.domain_name }} {{ config.opendkim_selector }}._domainkey.{{ config.domain_name }}

deploy-chatmail/src/deploy_chatmail/opendkim/opendkim.conf

@@ -1,7 +1,4 @@
-# This is a basic configuration for signing and verifying. It can easily be
-# adapted to suit a basic installation. See opendkim.conf(5) and
-# /usr/share/doc/opendkim/examples/opendkim.conf.sample for complete
-# documentation of available configuration parameters.
+# OpenDKIM configuration.
 
 Syslog			yes
 SyslogSuccess		yes
@@ -21,7 +18,9 @@ OversignHeaders		From
 # setup options can be found in /usr/share/doc/opendkim/README.opendkim.
 Domain			{{ config.domain_name }}
 Selector		{{ config.opendkim_selector }}
-KeyFile		/etc/dkimkeys/{{ config.opendkim_selector }}.private
+KeyFile		  /etc/dkimkeys/{{ config.opendkim_selector }}.private
+KeyTable          /etc/dkimkeys/KeyTable
+SigningTable      /etc/dkimkeys/SigningTable
 
 # In Debian, opendkim runs as user "opendkim". A umask of 007 is required when
 # using a local socket with MTAs that access the socket as a non-privileged

scripts/bench.sh

@@ -1,4 +1,4 @@
 #!/bin/bash
 set -e
 
-online-tests/venv/bin/pytest online-tests/benchmark.py -vrx 
+venv/bin/pytest online-tests/benchmark.py -vrx 

scripts/deploy.sh

@@ -1,10 +1,15 @@
 #!/usr/bin/env bash
-: ${CHATMAIL_DOMAIN:=c1.testrun.org}
-export CHATMAIL_DOMAIN
 
-chatmaild/venv/bin/python3 -m build -n --sdist chatmaild --outdir dist
+echo -----------------------------------------
+echo deploying to $CHATMAIL_DOMAIN 
+echo -----------------------------------------
 
-deploy-chatmail/venv/bin/pyinfra --ssh-user root "$CHATMAIL_DOMAIN" \
+echo WARNING: in five seconds deploy to $CHATMAIL_DOMAIN starts
+sleep 5
+
+venv/bin/python3 -m build -n --sdist chatmaild --outdir dist
+
+venv/bin/pyinfra --ssh-user root "$CHATMAIL_DOMAIN" \
     deploy-chatmail/src/deploy_chatmail/deploy.py
 
 rm -r dist/

scripts/generate-dns-zone.sh

@@ -0,0 +1,20 @@
+#!/bin/sh
+: ${CHATMAIL_DOMAIN:=c1.testrun.org}
+: ${CHATMAIL_SSH:=$CHATMAIL_DOMAIN}
+
+set -e
+SSH="ssh root@$CHATMAIL_SSH"
+EMAIL="root@$CHATMAIL_DOMAIN"
+ACME_ACCOUNT_URL="$($SSH -- acmetool account-url)"
+
+cat <<EOF
+$CHATMAIL_DOMAIN. MX 10 $CHATMAIL_DOMAIN.
+$CHATMAIL_DOMAIN. TXT "v=spf1 a:$CHATMAIL_DOMAIN -all"
+_dmarc.$CHATMAIL_DOMAIN. TXT "v=DMARC1;p=reject;rua=mailto:$EMAIL;ruf=mailto:$EMAIL;fo=1;adkim=r;aspf=r"
+_submission._tcp.$CHATMAIL_DOMAIN.  SRV 0 1 587 $CHATMAIL_DOMAIN.
+_submissions._tcp.$CHATMAIL_DOMAIN. SRV 0 1 465 $CHATMAIL_DOMAIN.
+_imap._tcp.$CHATMAIL_DOMAIN.        SRV 0 1 143 $CHATMAIL_DOMAIN.
+_imaps._tcp.$CHATMAIL_DOMAIN.       SRV 0 1 993 $CHATMAIL_DOMAIN.
+$CHATMAIL_DOMAIN. IN CAA 0 issue "letsencrypt.org; accounturi=$ACME_ACCOUNT_URL"
+EOF
+$SSH opendkim-genzone -F | sed 's/^;.*$//;/^$/d'

scripts/get_imap_capabilities.py

@@ -11,3 +11,4 @@ conn.login(f"imapcapa", "pass")
 status, res = conn.capability()
 for capa in sorted(res[0].decode().split()):
     print(capa)
+

scripts/init.sh

@@ -1,13 +1,8 @@
 #!/bin/sh
 set -e
-python3 -m venv deploy-chatmail/venv
-deploy-chatmail/venv/bin/pip install pyinfra pytest
-deploy-chatmail/venv/bin/pip install -e deploy-chatmail
-deploy-chatmail/venv/bin/pip install -e chatmaild
+python3 -m venv venv
+pip=venv/bin/pip
 
-python3 -m venv chatmaild/venv
-chatmaild/venv/bin/pip install --upgrade pytest build 'setuptools>=68'
-chatmaild/venv/bin/pip install -e chatmaild
-
-python3 -m venv online-tests/venv
-online-tests/venv/bin/pip install pytest pytest-timeout pdbpp deltachat 
+$pip install pyinfra pytest build 'setuptools>=68' tox deltachat
+$pip install -e deploy-chatmail 
+$pip install -e chatmaild 

scripts/measure_tls_and_logins.py

@@ -5,7 +5,7 @@ import imaplib
 
 domain = os.environ.get("CHATMAIL_DOMAIN", "c3.testrun.org")
 
-NUM_CONNECTIONS = 10
+NUM_CONNECTIONS=10
 
 conns = []
 
@@ -16,7 +16,7 @@ for i in range(NUM_CONNECTIONS):
     conns.append(conn)
 
 tlsdone = time.time()
-duration = tlsdone - start
+duration = tlsdone-start
 print(f"{duration}: TLS connections opening TLS connections")
 
 for i, conn in enumerate(conns):

scripts/test.sh

@@ -1,3 +1,4 @@
 #!/bin/bash
-chatmaild/venv/bin/pytest chatmaild/ $@
-online-tests/venv/bin/pytest online-tests/ -vrx --durations=5 $@
+venv/bin/tox -c chatmaild
+venv/bin/tox -c deploy-chatmail
+venv/bin/pytest tests/online -vrx --durations=5 $@

tests/chatmaild/conftest.py

@@ -1,9 +0,0 @@
-import pytest
-from chatmaild.database import Database
-
-
-@pytest.fixture()
-def db(tmpdir):
-    db_path = tmpdir / "passdb.sqlite"
-    print("database path:", db_path)
-    return Database(db_path)

tests/chatmaild/test_dictproxy.py

@@ -3,38 +3,43 @@ import os
 import pytest
 
 import chatmaild.dictproxy
-from chatmaild.dictproxy import DictProxy
-from chatmaild.database import DBError
+from chatmaild.dictproxy import get_user_data, lookup_passdb
+from chatmaild.database import Database, DBError
 
 
-@pytest.fixture
-def dictproxy(db, maildomain):
-    return DictProxy(db, maildomain)
+@pytest.fixture()
+def db(tmpdir):
+    db_path = tmpdir / "passdb.sqlite"
+    print("database path:", db_path)
+    return Database(db_path)
 
 
-def test_basic(dictproxy, tmpdir, monkeypatch):
-    monkeypatch.setattr(
-        chatmaild.dictproxy, "NOCREATE_FILE", tmpdir.join("nocreate").strpath
-    )
-    dictproxy.lookup_passdb("link2xt@c1.testrun.org", "asdf")
-    assert dictproxy.get_user_data("link2xt@c1.testrun.org")
+def test_basic(db):
+    chatmaild.dictproxy.NOCREATE_FILE = "/tmp/nocreate"
+    if os.path.exists(chatmaild.dictproxy.NOCREATE_FILE):
+        os.remove(chatmaild.dictproxy.NOCREATE_FILE)
+    lookup_passdb(db, "link2xt@c1.testrun.org", "Pieg9aeToe3eghuthe5u")
+    data = get_user_data(db, "link2xt@c1.testrun.org")
+    assert data
 
 
-def test_dont_overwrite_password_on_wrong_login(dictproxy):
+def test_dont_overwrite_password_on_wrong_login(db):
     """Test that logging in with a different password doesn't create a new user"""
-    res = dictproxy.lookup_passdb("newuser1@something.org", "kajdlkajsldk12l3kj1983")
+    res = lookup_passdb(db, "newuser1@something.org", "kajdlkajsldk12l3kj1983")
     assert res["password"]
-    res2 = dictproxy.lookup_passdb("newuser1@something.org", "kajdlqweqwe")
+    res2 = lookup_passdb(db, "newuser1@something.org", "kajdlqweqwe")
     # this function always returns a password hash, which is actually compared by dovecot.
     assert res["password"] == res2["password"]
 
 
-def test_nocreate_file(dictproxy, tmpdir, monkeypatch):
-    nocreate = tmpdir.join("nocreate")
-    monkeypatch.setattr(chatmaild.dictproxy, "NOCREATE_FILE", str(nocreate))
-    nocreate.write("")
-    dictproxy.lookup_passdb("newuser1@something.org", "kajdlqweqwe")
-    assert not dictproxy.get_user_data("newuser1@something.org")
+def test_nocreate_file(db):
+    chatmaild.dictproxy.NOCREATE_FILE = "/tmp/nocreate"
+    with open(chatmaild.dictproxy.NOCREATE_FILE, "w+") as f:
+        f.write("")
+    assert os.path.exists(chatmaild.dictproxy.NOCREATE_FILE)
+    lookup_passdb(db, "newuser1@something.org", "zequ0Aimuchoodaechik")
+    assert not get_user_data(db, "newuser1@something.org")
+    os.remove(chatmaild.dictproxy.NOCREATE_FILE)
 
 
 def test_db_version(db):

tests/chatmaild/test_filtermail.py

@@ -1,7 +1,13 @@
-from chatmaild.filtermail import check_encrypted, check_DATA, SendRateLimiter
+from chatmaild.filtermail import check_encrypted, check_DATA, SendRateLimiter, check_mdn
 import pytest
 
 
+@pytest.fixture
+def maildomain():
+    # let's not depend on a real chatmail instance for the offline tests below
+    return "chatmail.example.org"
+
+
 def test_reject_forged_from(maildata, gencreds):
     class env:
         mail_from = gencreds()[0]
@@ -35,8 +41,33 @@ def test_filtermail_encryption_detection(maildata):
     assert not check_encrypted(msg)
 
 
-def test_filtermail_mdn_is_not_encrypted(maildata):
-    assert not check_encrypted(maildata("mdn.eml"))
+def test_filtermail_is_mdn(maildata, gencreds):
+    from_addr = gencreds()[0]
+    to_addr = gencreds()[0] + ".other"
+    msg = maildata("mdn.eml", from_addr, to_addr)
+
+    class env:
+        mail_from = from_addr
+        rcpt_tos = [to_addr]
+        content = msg.as_bytes()
+
+    assert check_mdn(msg, env)
+    print(msg.as_string())
+    assert not check_DATA(env)
+
+
+def test_filtermail_to_multiple_recipients_no_mdn(maildata, gencreds):
+    from_addr = gencreds()[0]
+    to_addr = gencreds()[0] + ".other"
+    thirdaddr = gencreds()[0]
+    msg = maildata("mdn.eml", from_addr, to_addr)
+
+    class env:
+        mail_from = from_addr
+        rcpt_tos = [to_addr, thirdaddr]
+        content = msg.as_bytes()
+
+    assert not check_mdn(msg, env)
 
 
 def test_send_rate_limiter():

tests/conftest.py

@@ -290,7 +290,7 @@ class Remote:
 def maildata(request, gencreds):
     datadir = conftestdir.joinpath("mail-data")
 
-    def maildata(name, parsed=True, from_addr=None, to_addr=None):
+    def maildata(name, from_addr=None, to_addr=None):
         if from_addr is None:
             from_addr = gencreds()[0]
         if to_addr is None:

tests/mail-data/mdn.eml

@@ -1,6 +1,6 @@
 Subject: Message opened
-From: <barbaz@c2.testrun.org>
-To: <foobar@c2.testrun.org>
+From: <{from_addr}>
+To: <{to_addr}>
 Date: Sun, 15 Oct 2023 16:43:25 +0000
 Message-ID: <Mr.78MWtlV7RAi.goCFzBhCYfy@c2.testrun.org>
 Auto-Submitted: auto-replied

tests/online/test_0_login.py

@@ -23,6 +23,11 @@ def test_login_basic_functioning(imap_or_smtp, gencreds, lp):
     with pytest.raises(imap_or_smtp.AuthError):
         imap_or_smtp.login(user, password + "wrong")
 
+    lp.sec(f"creating users with a short password is not allowed")
+    user, _password = gencreds()
+    with pytest.raises(imap_or_smtp.AuthError):
+        imap_or_smtp.login(user, "admin")
+
 
 def test_login_same_password(imap_or_smtp, gencreds):
     """Test two different users logging in with the same password

tests/online/test_2_deltachat.py

@@ -1,3 +1,4 @@
+import time
 import random
 import pytest
 
@@ -81,3 +82,29 @@ class TestEndToEndDeltaChat:
         ch = ac2.qr_setup_contact(qr)
         assert ch.id >= 10
         ac1._evtracker.wait_securejoin_inviter_progress(1000)
+
+    def test_read_receipts_between_instances(self, cmfactory, lp, maildomain2):
+        ac1 = cmfactory.new_online_configuring_account(cache=False)
+        cmfactory.switch_maildomain(maildomain2)
+        ac2 = cmfactory.new_online_configuring_account(cache=False)
+        cmfactory.bring_accounts_online()
+
+        lp.sec("setup encrypted comms between ac1 and ac2 on different instances")
+        qr = ac1.get_setup_contact_qr()
+        ch = ac2.qr_setup_contact(qr)
+        msg = ac2.wait_next_incoming_message()
+        assert "verified" in msg.text
+
+        lp.sec("ac1 sends a message and ac2 marks it as seen")
+        chat = ac1.create_chat(ac2)
+        msg = chat.send_text("hi")
+        m = ac2.wait_next_incoming_message()
+        m.mark_seen()
+        # we can only indirectly wait for mark-seen to cause an smtp-error
+        lp.sec("try to wait for markseen to complete and check error states")
+        deadline = time.time() + 3.1
+        while time.time() < deadline:
+            msgs = m.chat.get_messages()
+            for msg in msgs:
+                assert "error" not in m.get_message_info()
+            time.sleep(1)