diff --git a/extensions/cookie/nsPermissionManager.cpp b/extensions/cookie/nsPermissionManager.cpp
index 2167506e983..bf871a626fa 100644
--- a/extensions/cookie/nsPermissionManager.cpp
+++ b/extensions/cookie/nsPermissionManager.cpp
@@ -94,8 +94,12 @@ GetPrincipal(const nsACString& aHost, uint32_t aAppId, bool aIsInBrowserElement,
   if (NS_FAILED(rv)) {
     // NOTE: most callers will end up here because we don't append "http://" for
     // hosts. It's fine to arbitrary use "http://" because, for those entries,
-    // we will actually just use the host.
-    rv = NS_NewURI(getter_AddRefs(uri), NS_LITERAL_CSTRING("http://") + aHost);
+    // we will actually just use the host. If we end up here, but the host looks
+    // like an email address, we use mailto: instead.
+    nsCString scheme = NS_LITERAL_CSTRING(
+      (aHost.FindChar('@') == -1) ? "http://" : "mailto:");
+
+    rv = NS_NewURI(getter_AddRefs(uri), scheme + aHost);
     NS_ENSURE_SUCCESS(rv, rv);
   }
 
diff --git a/extensions/cookie/test/unit/test_permmanager_mailto.js b/extensions/cookie/test/unit/test_permmanager_mailto.js
index 55499d63c38..2c05fefed23 100644
--- a/extensions/cookie/test/unit/test_permmanager_mailto.js
+++ b/extensions/cookie/test/unit/test_permmanager_mailto.js
@@ -15,13 +15,16 @@ function run_test() {
   Services.perms.add(uri, kType, kCapability);
   do_check_true(permission_exists(kTestAddr, kType, kCapability));
 
-  Services.perms.removeAll();
+  // remove the permission, and make sure it was removed
+  Services.perms.remove(kTestAddr, kType);
+  do_check_false(permission_exists(kTestAddr, kType, kCapability));
 
   uri = Services.io.newURI("mailto:" + kTestAddr, null, null);
   Services.perms.add(uri, kType, kCapability);
   do_check_true(permission_exists(kTestAddr, kType, kCapability));
 
-  Services.perms.removeAll();
+  Services.perms.remove(kTestAddr, kType);
+  do_check_false(permission_exists(kTestAddr, kType, kCapability));
 }
 
 function permission_exists(aHost, aType, aCapability) {