diff --git a/email/worker.go b/email/worker.go
index 881f9739d3534a34f2d055995602fcb5422741f9..288b3e0d528c5967200404969364083a275d9a5e 100644
--- a/email/worker.go
+++ b/email/worker.go
@@ -99,6 +99,11 @@ 	for _, addr := range cc {
 		rcpts = append(rcpts, addr.Address)
 	}
 
+	// Disallow content headers, signing/encrypting will change this
+	header.Del("Content-Transfer-Encoding")
+	header.Del("Content-Type")
+	header.Del("Content-Disposition")
+
 	if !header.Has("Message-Id") {
 		header.GenerateMessageID()
 	}