diff --git a/.eslintignore b/.eslintignore
index 0a47ebaba7..02b85a1ef0 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -50,8 +50,8 @@ mail/branding/nightly/pref/thunderbird-branding.js
 mail/branding/thunderbird/pref/thunderbird-branding.js
 # This file is split into two in order to keep it as a valid json file
 # for documentation purposes (policies.json) but to be accessed by the
-# code as a .jsm (schema.jsm)
-mail/components/enterprisepolicies/schemas/schema.jsm
+# code as a JS module (schema.sys.mjs)
+mail/components/enterprisepolicies/schemas/schema.sys.mjs
 mail/components/im/all-im.js
 mail/extensions/am-e2e/prefs/e2e-prefs.js
 mail/locales/en-US/all-l10n.js
diff --git a/.prettierignore b/.prettierignore
index 10efbeb0f7..b355666d2e 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -19,8 +19,8 @@ mailnews/mailnews.js
 
 # This file is split into two in order to keep it as a valid json file
 # for documentation purposes (policies.json) but to be accessed by the
-# code as a .jsm (schema.jsm).
-mail/components/enterprisepolicies/schemas/schema.jsm
+# code as a JS module (schema.sys.mjs).
+mail/components/enterprisepolicies/schemas/schema.sys.mjs
 
 # Third-party code.
 calendar/base/modules/Ical.jsm
diff --git a/mail/components/enterprisepolicies/content/aboutPolicies.js b/mail/components/enterprisepolicies/content/aboutPolicies.js
index fb3ad8a7e6..4615d9f462 100644
--- a/mail/components/enterprisepolicies/content/aboutPolicies.js
+++ b/mail/components/enterprisepolicies/content/aboutPolicies.js
@@ -8,8 +8,9 @@ const { XPCOMUtils } = ChromeUtils.importESModule(
   "resource://gre/modules/XPCOMUtils.sys.mjs"
 );
 
-XPCOMUtils.defineLazyModuleGetters(this, {
-  schema: "resource:///modules/policies/schema.jsm",
+const lazy = {};
+ChromeUtils.defineESModuleGetters(lazy, {
+  schema: "resource:///modules/policies/schema.sys.mjs",
 });
 
 function col(text, className) {
@@ -62,7 +63,7 @@ function generateActivePolicies(data) {
   for (let policyName in data) {
     const color_class = ++policy_count % 2 === 0 ? "even" : "odd";
 
-    if (schema.properties[policyName].type == "array") {
+    if (lazy.schema.properties[policyName].type == "array") {
       for (let count in data[policyName]) {
         let isFirstRow = count == 0;
         let isLastRow = count == data[policyName].length - 1;
@@ -78,7 +79,7 @@ function generateActivePolicies(data) {
           data[policyName].length > 1
         );
       }
-    } else if (schema.properties[policyName].type == "object") {
+    } else if (lazy.schema.properties[policyName].type == "object") {
       let count = 0;
       for (let obj in data[policyName]) {
         let isFirstRow = count == 0;
@@ -277,7 +278,7 @@ function generateDocumentation() {
     Certificates: "CertificatesDescription",
   };
 
-  for (let policyName in schema.properties) {
+  for (let policyName in lazy.schema.properties) {
     let main_tbody = document.createElement("tbody");
     main_tbody.classList.add("collapsible");
     main_tbody.addEventListener("click", function() {
@@ -295,32 +296,35 @@ function generateDocumentation() {
     sec_tbody.classList.add("content");
     sec_tbody.classList.add("content-style");
     let schema_row = document.createElement("tr");
-    if (schema.properties[policyName].properties) {
+    if (lazy.schema.properties[policyName].properties) {
       let column = col(
-        JSON.stringify(schema.properties[policyName].properties, null, 1),
+        JSON.stringify(lazy.schema.properties[policyName].properties, null, 1),
         "schema"
       );
       column.colSpan = "2";
       schema_row.appendChild(column);
       sec_tbody.appendChild(schema_row);
-    } else if (schema.properties[policyName].items) {
+    } else if (lazy.schema.properties[policyName].items) {
       let column = col(
-        JSON.stringify(schema.properties[policyName], null, 1),
+        JSON.stringify(lazy.schema.properties[policyName], null, 1),
         "schema"
       );
       column.colSpan = "2";
       schema_row.appendChild(column);
       sec_tbody.appendChild(schema_row);
     } else {
-      let column = col("type: " + schema.properties[policyName].type, "schema");
+      let column = col(
+        "type: " + lazy.schema.properties[policyName].type,
+        "schema"
+      );
       column.colSpan = "2";
       schema_row.appendChild(column);
       sec_tbody.appendChild(schema_row);
-      if (schema.properties[policyName].enum) {
+      if (lazy.schema.properties[policyName].enum) {
         let enum_row = document.createElement("tr");
         column = col(
           "enum: " +
-            JSON.stringify(schema.properties[policyName].enum, null, 1),
+            JSON.stringify(lazy.schema.properties[policyName].enum, null, 1),
           "schema"
         );
         column.colSpan = "2";
diff --git a/mail/components/enterprisepolicies/schemas/moz.build b/mail/components/enterprisepolicies/schemas/moz.build
index 45c242ed1e..658f0b1ed7 100644
--- a/mail/components/enterprisepolicies/schemas/moz.build
+++ b/mail/components/enterprisepolicies/schemas/moz.build
@@ -8,5 +8,5 @@ with Files("**"):
     BUG_COMPONENT = ("Thunderbird", "OS Integration")
 
 EXTRA_PP_JS_MODULES.policies += [
-    "schema.jsm",
+    "schema.sys.mjs",
 ]
diff --git a/mail/components/enterprisepolicies/schemas/schema.jsm b/mail/components/enterprisepolicies/schemas/schema.sys.mjs
similarity index 53%
rename from mail/components/enterprisepolicies/schemas/schema.jsm
rename to mail/components/enterprisepolicies/schemas/schema.sys.mjs
index fba69c56c9..671a8cfca1 100644
--- a/mail/components/enterprisepolicies/schemas/schema.jsm
+++ b/mail/components/enterprisepolicies/schemas/schema.sys.mjs
@@ -2,9 +2,15 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-"use strict";
-
-const EXPORTED_SYMBOLS = ["schema"];
-
-var schema =
+const initialSchema =
 #include policies-schema.json
+
+export let schema = initialSchema;
+
+export function modifySchemaForTests(customSchema) {
+  if (customSchema) {
+    schema = customSchema;
+  } else {
+    schema = initialSchema;
+  }
+}
diff --git a/mail/components/enterprisepolicies/tests/xpcshell/test_sorted_alphabetically.js b/mail/components/enterprisepolicies/tests/xpcshell/test_sorted_alphabetically.js
index b56a69a1b3..088e4fcb7e 100644
--- a/mail/components/enterprisepolicies/tests/xpcshell/test_sorted_alphabetically.js
+++ b/mail/components/enterprisepolicies/tests/xpcshell/test_sorted_alphabetically.js
@@ -19,8 +19,8 @@ function checkArrayIsSorted(array, msg) {
 }
 
 add_task(async function test_policies_sorted() {
-  let { schema } = ChromeUtils.import(
-    "resource:///modules/policies/schema.jsm"
+  let { schema } = ChromeUtils.importESModule(
+    "resource:///modules/policies/schema.sys.mjs"
   );
   let { Policies } = ChromeUtils.importESModule(
     "resource:///modules/policies/Policies.sys.mjs"
@@ -37,8 +37,8 @@ add_task(async function test_policies_sorted() {
 });
 
 add_task(async function check_naming_conventions() {
-  let { schema } = ChromeUtils.import(
-    "resource:///modules/policies/schema.jsm"
+  let { schema } = ChromeUtils.importESModule(
+    "resource:///modules/policies/schema.sys.mjs"
   );
   equal(
     Object.keys(schema.properties).some(key => key.includes("__")),
diff --git a/tools/esmify/mach_commands.py b/tools/esmify/mach_commands.py
index 311bd82922..fb02f4982e 100644
--- a/tools/esmify/mach_commands.py
+++ b/tools/esmify/mach_commands.py
@@ -56,7 +56,7 @@ excluded_from_imports_prefix = list(
             "mail/app/profile/all-thunderbird.js",
             "mail/branding/thunderbird/pref/thunderbird-branding.js",
             "mail/components/compose/composer.js",
-            "mail/components/enterprisepolicies/schemas/schema.jsm",
+            "mail/components/enterprisepolicies/schemas/schema.sys.mjs",
             "mail/locales/en-US/all-l10n.js",
             "mail/extensions/am-e2e/prefs/e2e-prefs.js",
             "mailnews/extensions/mdn/mdn.js",
diff --git a/tools/esmify/map.json b/tools/esmify/map.json
index af34d0bb4c..d3ee88359b 100644
--- a/tools/esmify/map.json
+++ b/tools/esmify/map.json
@@ -415,7 +415,6 @@
   "resource:///modules/matrixTextForEvent.jsm": "comm/chat/protocols/matrix/matrixTextForEvent.jsm",
   "resource:///modules/mimeParser.jsm": "comm/mailnews/mime/src/mimeParser.jsm",
   "resource:///modules/odnoklassniki.jsm": "comm/chat/protocols/odnoklassniki/odnoklassniki.jsm",
-  "resource:///modules/policies/schema.jsm": "comm/mail/components/enterprisepolicies/schemas/schema.jsm",
   "resource:///modules/sax.jsm": "comm/chat/protocols/xmpp/sax.jsm",
   "resource:///modules/socket.jsm": "comm/chat/modules/socket.jsm",
   "resource:///modules/twitter.jsm": "comm/chat/protocols/twitter/twitter.jsm",