diff --git a/application/src/main/java/org/thingsboard/server/controller/AdminController.java b/application/src/main/java/org/thingsboard/server/controller/AdminController.java
index 154e349fdb..371ca4d3e4 100644
--- a/application/src/main/java/org/thingsboard/server/controller/AdminController.java
+++ b/application/src/main/java/org/thingsboard/server/controller/AdminController.java
@@ -130,7 +130,7 @@ public class AdminController extends BaseController {
             @PathVariable("key") String key) throws ThingsboardException {
         accessControlService.checkPermission(getCurrentUser(), Resource.ADMIN_SETTINGS, Operation.READ);
         AdminSettings adminSettings = checkNotNull(adminSettingsService.findAdminSettingsByKey(TenantId.SYS_TENANT_ID, key), "No Administration settings found for key: " + key);
-        if (adminSettings.getKey().equals("mail")) {
+        if (adminSettings.getKey().equals(MAIL_SETTINGS_KEY)) {
             ((ObjectNode) adminSettings.getJsonValue()).remove("password");
             ((ObjectNode) adminSettings.getJsonValue()).remove("refreshToken");
         }
@@ -149,7 +149,7 @@ public class AdminController extends BaseController {
         accessControlService.checkPermission(getCurrentUser(), Resource.ADMIN_SETTINGS, Operation.WRITE);
         adminSettings.setTenantId(getTenantId());
         adminSettings = checkNotNull(adminSettingsService.saveAdminSettings(TenantId.SYS_TENANT_ID, adminSettings));
-        if (adminSettings.getKey().equals("mail")) {
+        if (adminSettings.getKey().equals(MAIL_SETTINGS_KEY)) {
             mailService.updateMailConfiguration();
             ((ObjectNode) adminSettings.getJsonValue()).remove("password");
             ((ObjectNode) adminSettings.getJsonValue()).remove("refreshToken");
@@ -212,9 +212,9 @@ public class AdminController extends BaseController {
             @RequestBody AdminSettings adminSettings) throws ThingsboardException {
         accessControlService.checkPermission(getCurrentUser(), Resource.ADMIN_SETTINGS, Operation.READ);
         adminSettings = checkNotNull(adminSettings);
-        if (adminSettings.getKey().equals("mail")) {
+        if (adminSettings.getKey().equals(MAIL_SETTINGS_KEY)) {
             if (adminSettings.getJsonValue().has("enableOauth2") && adminSettings.getJsonValue().get("enableOauth2").asBoolean()) {
-                AdminSettings mailSettings = checkNotNull(adminSettingsService.findAdminSettingsByKey(TenantId.SYS_TENANT_ID, "mail"));
+                AdminSettings mailSettings = checkNotNull(adminSettingsService.findAdminSettingsByKey(TenantId.SYS_TENANT_ID, MAIL_SETTINGS_KEY));
                 JsonNode refreshToken = mailSettings.getJsonValue().get("refreshToken");
                 if (refreshToken == null) {
                     throw new ThingsboardException("Refresh token was not generated. Please, generate refresh token.", ThingsboardErrorCode.GENERAL);
@@ -223,7 +223,7 @@ public class AdminController extends BaseController {
                 settings.put("refreshToken", refreshToken.asText());
             } else {
                 if (!adminSettings.getJsonValue().has("password")) {
-                    AdminSettings mailSettings = checkNotNull(adminSettingsService.findAdminSettingsByKey(TenantId.SYS_TENANT_ID, "mail"));
+                    AdminSettings mailSettings = checkNotNull(adminSettingsService.findAdminSettingsByKey(TenantId.SYS_TENANT_ID, MAIL_SETTINGS_KEY));
                     ((ObjectNode) adminSettings.getJsonValue()).put("password", mailSettings.getJsonValue().get("password").asText());
                 }
             }