diff --git a/scripts/_email_exclusions.py b/scripts/_email_exclusions.py
new file mode 100644
index 0000000..85ee257
--- /dev/null
+++ b/scripts/_email_exclusions.py
@@ -0,0 +1,45 @@
+"""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 single biggest lever is
+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.
+
+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",
+})
+
+# 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
+
+
+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
diff --git a/scripts/build_trucking_campaigns.py b/scripts/build_trucking_campaigns.py
index 782e7a9..1a07df7 100644
--- a/scripts/build_trucking_campaigns.py
+++ b/scripts/build_trucking_campaigns.py
@@ -31,6 +31,8 @@ from datetime import date, datetime, timedelta, timezone
 
 import psycopg2
 
+from scripts._email_exclusions import BLOCKED_EMAIL_DOMAINS
+
 LOG = logging.getLogger("build_trucking_campaigns")
 
 # ── Listmonk ──────────────────────────────────────────────────────────────────
@@ -155,13 +157,6 @@ USABLE_FILTER = (
     "('smtp_valid','catch_all_domain','catch_all_detected'))"
 )
 
-BLOCKED_EMAIL_DOMAINS = (
-    "aol.com",
-    "yahoo.com",
-    "ymail.com",
-    "rocketmail.com",
-)
-
 DB_URL = os.getenv("DATABASE_URL", "")
 
 
diff --git a/scripts/populate_new_carrier_startup_campaign.py b/scripts/populate_new_carrier_startup_campaign.py
index 640e0d0..9727990 100644
--- a/scripts/populate_new_carrier_startup_campaign.py
+++ b/scripts/populate_new_carrier_startup_campaign.py
@@ -31,6 +31,8 @@ from typing import Any
 import psycopg2
 import psycopg2.extras
 
+from scripts._email_exclusions import BLOCKED_EMAIL_DOMAINS
+
 LOG = logging.getLogger("populate_new_carrier_startup_campaign")
 
 LISTMONK_URL = os.getenv("LISTMONK_URL", "https://lists.performancewest.net").rstrip("/")
@@ -39,7 +41,6 @@ LISTMONK_PASS = os.getenv("LISTMONK_PASS", "6X1rKPea61N4rZ1S65Hx5zvqzbCj30F6nvEe
 LIST_NAME = os.getenv("NEW_CARRIER_LIST_NAME", "FMCSA Trucking - New Carrier Missing Startup Items")
 DATABASE_URL = os.getenv("DATABASE_URL", "")
 
-BLOCKED_EMAIL_DOMAINS = {"aol.com", "yahoo.com", "ymail.com", "rocketmail.com"}
 STARTUP_SERVICE_SLUGS = {
     "boc3-filing",
     "ucr-registration",