diff --git a/rules/first-party.list b/rules/first-party.list
index e9152ad..8bd2045 100644
--- a/rules/first-party.list
+++ b/rules/first-party.list
@@ -72,3 +72,6 @@ exactag.com
 ad-cloud.jp
 # Pardot
 pardot.com
+# Fathom
+# https://usefathom.com/docs/settings/custom-domains
+starman.fathomdns.com
diff --git a/tests/first-party.csv b/tests/first-party.csv
index 26c93d4..e8bbdda 100644
--- a/tests/first-party.csv
+++ b/tests/first-party.csv
@@ -22,3 +22,4 @@ https://www.seatadvisor.com/,,marketing.seatadvisor.com,Sugar Market (Salesfusio
 https://www.tchibo.de/,,tagm.tchibo.de,Exactag
 https://www.tchibo.de/,,tagm.tchibo.de,Exactag
 https://www.bouygues-immobilier.com/,,go.bouygues-immobilier.fr,Pardot
+https://caddyserver.com/,,mule.caddysever.com,Fathom