diff --git a/src/validators/email.py b/src/validators/email.py
index 46cc594..3b59d8a 100644
--- a/src/validators/email.py
+++ b/src/validators/email.py
@@ -91,8 +91,8 @@ def email(
             + r"(\.[\u0100-\u017F\u0180-\u024F\u00A0-\u00FF0-9a-z!#$%&'*+/=?^_`{}|~\-]+)*$"
             # quoted-string
             + r'|^"('
-            + r"[\u0100-\u017F\u0180-\u024F\u00A0-\u00FF\001-\010\013\014\016-\037"
-            + r"!#-\[\]-\177]|\\[\011.]"
+            + r"[\u0100-\u017F\u0180-\u024F\u00A0-\u00FF"
+            + r"!#-\[\]-~]|\\[\011.]"
             + r')*")$',
             username_part,
             re.IGNORECASE,
diff --git a/tests/test_email_control_character.py b/tests/test_email_control_character.py
new file mode 100644
index 0000000..2373d11
--- /dev/null
+++ b/tests/test_email_control_character.py
@@ -0,0 +1,20 @@
+"""HU-02: reject ASCII control characters in quoted SMTP local parts."""
+
+# external
+import pytest
+
+import validators
+
+
+@pytest.mark.parametrize(
+    "control_code",
+        [1, 2, 7, 11, 12, 14, 27, 31, 127],
+)
+
+def test_email_rejects_control_characters(control_code: int):
+    """Reject selected ASCII control characters in quoted local parts."""
+    email = f'"user{chr(control_code)}name"@example.com'
+
+    result = validators.email(email)
+
+    assert isinstance(result, validators.ValidationError), repr(result)
diff --git a/tests/test_email_ipv6_literal.py b/tests/test_email_ipv6_literal.py
new file mode 100644
index 0000000..a4f208a
--- /dev/null
+++ b/tests/test_email_ipv6_literal.py
@@ -0,0 +1,20 @@
+"""HU-02: accept the IPv6: prefix in an SMTP address literal."""
+
+# external
+import pytest
+
+import validators
+
+
+@pytest.mark.parametrize(
+    ("email",),
+    [
+        ("usuario@[IPv6:2001:db8::1]", ),
+    ],
+)
+def test_email_accepts_ipv6_literal_with_prefix(email: str):
+    """Email accepts ipv6 literal with prefix."""
+    result = validators.email(
+        email, ipv6_address=True
+    )
+    assert result is True, repr(result)
diff --git a/tests/test_email_quoted_at_sign.py b/tests/test_email_quoted_at_sign.py
new file mode 100644
index 0000000..02d7b1f
--- /dev/null
+++ b/tests/test_email_quoted_at_sign.py
@@ -0,0 +1,18 @@
+"""HU-02: accept @ inside a quoted local part."""
+
+# external
+import pytest
+
+import validators
+
+
+@pytest.mark.parametrize(
+    ("email",),
+    [
+        ('"user@name"@example.com', ),
+    ],
+)
+def test_email_accepts_at_sign_inside_quoted_local_part(email: str):
+    """The email accepts at sign inside quoted local part character."""
+    result = validators.email(email)
+    assert result is True, repr(result)
diff --git a/tests/test_ipv4_strict_cidr.py b/tests/test_ipv4_strict_cidr.py
new file mode 100644
index 0000000..68bdf32
--- /dev/null
+++ b/tests/test_ipv4_strict_cidr.py
@@ -0,0 +1,18 @@
+"""HU-04: require a prefix length in the documented strict CIDR mode."""
+
+# external
+import pytest
+
+import validators
+
+
+@pytest.mark.parametrize(
+    ("ip",),
+    [
+        ("192.168.1.0/255.255.255.0", ),
+    ],
+)
+def test_ipv4_strict_cidr_rejects_dotted_netmask(ip: str):
+    """The network is valid, but its representation is not CIDR prefix notation."""
+    result = validators.ipv4(ip, strict=True)
+    assert isinstance(result, validators.ValidationError), repr(result)
diff --git a/tests/test_ipv6_brackets.py b/tests/test_ipv6_brackets.py
new file mode 100644
index 0000000..908cdd4
--- /dev/null
+++ b/tests/test_ipv6_brackets.py
@@ -0,0 +1,21 @@
+"""HU-04: proposed enhancement; brackets are URL host syntax.
+
+This test expresses a new requirement, not a defect in the current contract.
+"""
+
+# external
+import pytest
+
+import validators
+
+
+@pytest.mark.parametrize(
+    ("ip",),
+    [
+        ("[2001:db8::1]", ),
+    ],
+)
+def test_ipv6_accepts_address_in_brackets(ip: str):
+    """Accept iv6 address in brackets."""
+    result = validators.ipv6(ip)
+    assert result is True, repr(result)