"""Shared recipient-domain exclusions for outbound cold-email campaigns.

We self-host our MTA (transactional relays like SES forbid cold email), so we
must protect our sending-IP reputation manually. The two biggest levers:

  1. NOT mailing the Yahoo/Verizon-Media family: those providers aggressively
     defer cold senders with "unexpected volume / user complaints" 421
     responses, which poisons the IP for every other provider too.
  2. NOT mailing Google CONSUMER mailboxes (gmail.com etc.) from a cold/warming
     IP: Google hard-rejects them with 550-5.7.1 "this message is likely
     unsolicited mail", and those rejections are reputation-damaging. (On
     2026-06-08 a warmup audit found gmail.com alone was 77% of our 550-5.7.1
     blocks -- 427 of 556.) Custom domains hosted on Google Workspace are a
     smaller, MX-only signal handled separately in the per-vertical builders.

Keep this list authoritative and import it everywhere we build audiences.
"""

from __future__ import annotations

# Yahoo / Verizon Media operates ALL of these consumer domains. Legacy AT&T and
# Frontier consumer mail was handed off to Yahoo's infrastructure as well.
YAHOO_FAMILY_DOMAINS: frozenset[str] = frozenset({
    # Yahoo / AOL core
    "yahoo.com", "yahoo.com.mx", "yahoo.es", "yahoo.it", "yahoo.ca",
    "myyahoo.com", "ymail.com", "rocketmail.com",
    "aol.com", "aol.com.mx", "aim.com", "love.com", "games.com", "wow.com",
    "netscape.net", "netscape.com", "cs.com", "compuserve.com",
    # AT&T family (Yahoo-hosted)
    "att.net", "sbcglobal.net", "bellsouth.net", "pacbell.net",
    "ameritech.net", "swbell.net", "snet.net", "flash.net", "prodigy.net",
    "wans.net", "nvbell.net",
    # Verizon family (Yahoo-hosted)
    "verizon.net", "verizongni.com", "bellatlantic.net",
    # Frontier (Yahoo-hosted)
    "frontier.com", "frontiernet.net",
})

# Google consumer mailboxes. Google's cold-IP spam filter (550-5.7.1) is the
# strictest of the big providers; consumer gmail accounts have the highest
# complaint sensitivity. We hold these out of cold/warmup sends. (This is the
# domain-string layer; custom domains silently on Google Workspace need an MX
# lookup and are handled in the per-vertical builders, e.g. the healthcare
# mx_provider flag.)
GOOGLE_CONSUMER_DOMAINS: frozenset[str] = frozenset({
    "gmail.com", "googlemail.com",
})

# Microsoft consumer mailboxes (Outlook.com / Hotmail). Microsoft's cold-IP
# filtering (SmartScreen) tends to silently route cold B2B mail to Junk or
# soft-defer rather than hard-bounce, so it is less visible than Google's
# 550-5.7.1 but still a reputation drag (low engagement, spam-folder placement)
# on a warming IP. These are consumer mailboxes, not real B2B carrier contacts,
# so we hold them out of cold/warmup sends like the other consumer providers.
MICROSOFT_CONSUMER_DOMAINS: frozenset[str] = frozenset({
    "hotmail.com", "outlook.com", "live.com", "msn.com", "hotmail.co.uk",
    "hotmail.fr", "live.co.uk", "outlook.es", "passport.com", "windowslive.com",
})

# The full set of consumer domains we refuse to cold-mail. Extend here as we
# discover other reputation-sensitive providers.
BLOCKED_EMAIL_DOMAINS: frozenset[str] = (
    YAHOO_FAMILY_DOMAINS | GOOGLE_CONSUMER_DOMAINS | MICROSOFT_CONSUMER_DOMAINS
)


def domain_of(email: str) -> str:
    """Return the lowercased domain part of an email, or '' if malformed."""
    if "@" not in email:
        return ""
    return email.rsplit("@", 1)[-1].strip().lower()


def is_blocked(email: str) -> bool:
    return domain_of(email) in BLOCKED_EMAIL_DOMAINS