email.utils.parseaddr rejects a valid quoted local part containing '['

[augusto-rehfeldt]

Bug report

Bug description:

Documented behaviour: email.utils.formataddr documentation and docstring: "The inverse of parseaddr(), this takes a 2-tuple of the form (realname, email_address) and returns the string value suitable for an RFC 2822 From, To or Cc header."

Expected: ('Alice', '"a[b"@example.com')

Actual: ('', '')

import email.utils as e
import re

pair = ('Alice', '"a[b"@example.com')
name, address = pair
# RFC 2822 quoted-string qtext permits "["; example.com is a valid domain.
if not (re.fullmatch(r'[A-Za-z]+', name) and
        re.fullmatch(r'"[\x21\x23-\x5b\x5d-\x7e]+"@example\.com', address)):
    print('REFUTATION REJECTED: input validity not established')
else:
    expected = (name, address)  # Independently derived from the inverse promise.
    actual = e.parseaddr(e.formataddr(pair))
    if actual != expected:
        print('REFUTATION CONFIRMED:', pair, 'actual:', actual, 'expected:', expected)
    else:
        print('REFUTATION REJECTED: documented round trip succeeds')

Output on Python 3.14.6 (Windows-11-10.0.26220-SP0), standard library email.utils:

REFUTATION CONFIRMED: ('Alice', '"a[b"@example.com') actual: ('', '') expected: ('Alice', '"a[b"@example.com')

This report was found and written by an automated property-testing tool I run (bugforge). The reproducer above was executed and its output is pasted unedited; no person reviewed the report before it was filed. The search script is in https://github.com/augusto-rehfeldt/bugforge-results/tree/main/email.utils-20261003-021105-c1

CPython versions tested on:

3.14

Operating systems tested on:

Windows

[ZeroIntensity]

See #158748 (comment).