diff --git a/scripts/_email_exclusions.py b/scripts/_email_exclusions.py
index ded5fa1..fe8e0a5 100644
--- a/scripts/_email_exclusions.py
+++ b/scripts/_email_exclusions.py
@@ -46,9 +46,22 @@ 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
+BLOCKED_EMAIL_DOMAINS: frozenset[str] = (
+    YAHOO_FAMILY_DOMAINS | GOOGLE_CONSUMER_DOMAINS | MICROSOFT_CONSUMER_DOMAINS
+)
 
 
 def domain_of(email: str) -> str: