Read false values of the command-line tool's environment variables as false

CHANGELOG.md

@@ -4,6 +4,7 @@ In Development
 * Python 3.8 and 3.9 are no longer supported.
 * The `original` field of the returned validated email object incorrectly un-escaped the local part of the email address. Now it returns the original address, without any display name, as passed to validate_email.
 * add support python3.15
+* The command-line tool now reads `0`, `false`, `no` and `off` in its environment variables (e.g. `CHECK_DELIVERABILITY=0`) as false. Previously any non-empty value turned the option on.
 * The IPv6 tag of a domain literal is now case-insensitive, as in the RFCs, so `me@[ipv6:::1]` is accepted (and normalized to `me@[IPv6:::1]`) when `allow_domain_literal=True`.
 
 2.3.0 (August 26, 2025)

email_validator/__main__.py

@@ -33,7 +33,8 @@ def main(dns_resolver: Optional[_Resolver] = None) -> None:
                     'ALLOW_DISPLAY_NAME',
                     'GLOBALLY_DELIVERABLE', 'CHECK_DELIVERABILITY', 'TEST_ENVIRONMENT'):
         if varname in os.environ:
-            options[varname.lower()] = bool(os.environ[varname])
+            # Any non-empty string is truthy, so the usual false values are recognized explicitly.
+            options[varname.lower()] = os.environ[varname].strip().lower() not in ('', '0', 'false', 'no', 'off')
     for varname in ('DEFAULT_TIMEOUT',):
         if varname in os.environ:
             options[varname.lower()] = float(os.environ[varname])

tests/test_main.py

@@ -81,6 +81,19 @@ def test_main_multi_input(monkeypatch: pytest.MonkeyPatch, capsys: pytest.Captur
     assert test_cases[3] in stdout
 
 
+@pytest.mark.parametrize(
+    ('value', 'allowed'),
+    [('1', True), ('true', True), ('yes', True), ('0', False), ('false', False), ('FALSE', False), ('no', False), ('', False)]
+)
+def test_main_boolean_environment_variable(monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str],
+                                           value: str, allowed: bool) -> None:
+    monkeypatch.setenv('ALLOW_DOMAIN_LITERAL', value)
+    monkeypatch.setattr('sys.argv', ['email_validator', 'me@[127.0.0.1]'])
+    validator_command_line_tool(dns_resolver=RESOLVER)
+    stdout, _ = capsys.readouterr()
+    assert ('A bracketed IP address after the @-sign is not allowed here.' in stdout) is not allowed
+
+
 def test_bytes_input() -> None:
     input_email = b"testaddr@example.tld"
     valid_email = validate_email(input_email, check_deliverability=False)