diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index aab4196..bcdbdfc 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -37,6 +37,32 @@ jobs:
         with:
           command: test
           args: --verbose --all-features
+  integration-test:
+    name: Integration test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Apt update
+        run: sudo apt update
+      - name: Install Python
+        run: sudo apt install -y python3
+      - name: Install OpenSMTPD
+        run: sudo apt install -y opensmtpd
+      - name: Stop OpenSMTPD
+        run: sudo systemctl stop opensmtpd.service
+      - name: Install Rust stable
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          override: true
+          profile: minimal
+      - name: Run cargo build
+        uses: actions-rs/cargo@v1
+        with:
+          command: build
+          args: --verbose --all-features
+      - name: Run the integration test
+        run: ./start_test.py
   cargo-fmt:
     name: Cargo fmt
     runs-on: ubuntu-latest
diff --git a/start_test.py b/start_test.py
new file mode 100755
index 0000000..4f4bbdc
--- /dev/null
+++ b/start_test.py
@@ -0,0 +1,158 @@
+#!/usr/bin/env python3
+
+import os
+import pathlib
+import shutil
+import smtplib
+import stat
+import subprocess
+import sys
+import tempfile
+import time
+
+ADDR_FROM = "test.from@example.org"
+DEFAULT_PORT = 2525
+
+
+def fail(message):
+    print(message, file=sys.stderr)
+    sys.exit(1)
+
+
+def cp_tmp_file(path, executable=False):
+    file = tempfile.NamedTemporaryFile(suffix=f"-{path.name}", delete=False)
+    with open(path, mode="rb") as f:
+        file.write(f.read())
+        file.flush()
+    flags = stat.S_IRUSR | stat.S_IWUSR | stat.S_IRGRP | stat.S_IROTH
+    if executable:
+        flags = flags | stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
+    os.chmod(file.name, flags)
+    file.close()
+    return file
+
+
+def get_filter_path(test_dir, target):
+    filter_path = test_dir / "target" / target / "filter-sake"
+    filter_path = cp_tmp_file(filter_path, executable=True).name
+    return filter_path
+
+
+def get_opensmtpd_config(port, filter_exe, maildir_path):
+    cfg_content = f"""# OpenSMTPD test configuration
+
+# DKIM filter
+filter "sake" proc-exec "{filter_exe} --address 'a@example.org:11voiefK5PgCX5F1TTcuoQ==' --address 'b:11voiefK5PgCX5F1TTcuoQ=='"
+
+# Tables
+table domains {{ "example.org", "example.com" }}
+table vusers {{ "test" = "1000:100:{maildir_path}", "b" = "1000:100:{maildir_path}" }}
+table aliases {{ "a" = "test" }}
+
+# Listening
+listen on 127.0.0.1 port {port} hostname localhost filter "sake"
+listen on ::1 port {port} hostname localhost filter "sake"
+
+# Delivering
+action "deliver" maildir userbase <vusers> alias <aliases>
+match from any for domain <domains> action "deliver"
+"""
+    cfg_file = tempfile.NamedTemporaryFile(prefix="smtpd-", suffix=".conf")
+    cfg_file.write(cfg_content.encode())
+    cfg_file.flush()
+    return cfg_file
+
+
+def send_msg(smtp, to_addr, is_valid):
+    msg = f"From: {ADDR_FROM}\r\nTo: {to_addr}\r\n\r\ntest"
+    try:
+        smtp.sendmail(ADDR_FROM, to_addr, msg)
+        if not is_valid:
+            print(f"{to_addr}: accepted: error")
+            return False
+        print(f"{to_addr}: accepted: ok")
+    except smtplib.SMTPRecipientsRefused:
+        if is_valid:
+            print(f"{to_addr}: refused: error")
+            return False
+        print(f"{to_addr}: refused: ok")
+    return True
+
+
+def start_opensmtpd(cfg_path):
+    args = [
+        shutil.which("sudo"),
+        shutil.which("smtpd"),
+        "-d",
+        "-f",
+        cfg_path.name,
+    ]
+    p = subprocess.Popen(
+        args,
+        stdin=subprocess.DEVNULL,
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.DEVNULL,
+    )
+    time.sleep(5)
+    return p.pid
+
+
+def kill_opensmtpd(pid):
+    if pid is not None:
+        subprocess.Popen([shutil.which("sudo"), shutil.which("kill"), f"{pid}"])
+
+
+def get_maildir():
+    maildir = tempfile.TemporaryDirectory(prefix="Maildir_")
+    flags = (
+        stat.S_IRUSR
+        | stat.S_IWUSR
+        | stat.S_IXUSR
+        | stat.S_IRGRP
+        | stat.S_IWGRP
+        | stat.S_IXGRP
+        | stat.S_IROTH
+        | stat.S_IWOTH
+        | stat.S_IXOTH
+    )
+    os.chmod(maildir.name, flags)
+    return maildir
+
+
+def start_tests(test_dir, smtp_port):
+    to_addrs = [
+        ("test@example.org", True),
+        ("test@nope.example.org", False),
+        ("a@example.com", True),
+        ("a@example.org", False),
+        ("a+invalid@example.org", False),
+        ("a+invalid+input@example.org", False),
+        ("b@example.org", False),
+    ]
+    maildir = get_maildir()
+    filter_cmd = get_filter_path(test_dir, "debug")
+    pid_smtpd = None
+    has_errors = False
+    try:
+        cfg_path = get_opensmtpd_config(smtp_port, filter_cmd, maildir.name)
+        pid_smtpd = start_opensmtpd(cfg_path)
+        with smtplib.SMTP(host="localhost", port=smtp_port) as smtp_session:
+            for addr, is_valid in to_addrs:
+                if not send_msg(smtp_session, addr, is_valid):
+                    has_errors = True
+    except Exception:
+        kill_opensmtpd(pid_smtpd)
+        raise
+    kill_opensmtpd(pid_smtpd)
+    if has_errors:
+        fail("test failed")
+
+
+def main():
+    test_dir = pathlib.Path(__file__).parent.resolve()
+    os.chdir(test_dir.parent)
+    start_tests(test_dir, DEFAULT_PORT)
+
+
+if __name__ == "__main__":
+    main()