diff --git a/detection-rules/headers_recipient_sld_matches_mailer.yml b/detection-rules/headers_recipient_sld_matches_mailer.yml
deleted file mode 100644
index 9bb86fe6a0b..00000000000
--- a/detection-rules/headers_recipient_sld_matches_mailer.yml
+++ /dev/null
@@ -1,13 +0,0 @@
-name: "Headers: Recipient SLD matches X-mailer"
-description: "This rule flags messages where the recipients Single Level Domain (SLD) is an exact match of the X-mailer value. This has been observed in Credential Phishing campaigns. \n"
-type: "rule"
-severity: "medium"
-source: |
-  type.inbound and any(recipients.to, .email.domain.sld == headers.mailer)
-attack_types:
-  - "Credential Phishing"
-detection_methods:
-  - "Header analysis"
-id: "0eca4648-0e8a-5602-8e7b-d2233c983a33"
-testing_pr: 669
-testing_sha: 7dda1aa68e412d27faecf2cf2c7851146fb11ea4