diff --git a/assets/js/src/settings/pages/key_activation/index.tsx b/assets/js/src/settings/pages/key_activation/index.tsx
index 31285daf1f..1e4e209dd3 100644
--- a/assets/js/src/settings/pages/key_activation/index.tsx
+++ b/assets/js/src/settings/pages/key_activation/index.tsx
@@ -36,7 +36,7 @@ export default function KeyActivation() {
     MailPoet.Modal.loading(false);
     if (isTrusted) {
       const authorizedAddressNeeded = !senderAddress || unauthorizedAddresses;
-      if (mssStatus === 'valid_mss_active' && authorizedAddressNeeded) {
+      if (mssStatus === MssStatus.VALID_MSS_ACTIVE && authorizedAddressNeeded) {
         setState({ showFromAddressModal: true });
       }
     }
diff --git a/assets/js/src/settings/pages/key_activation/messages/mss_messages.tsx b/assets/js/src/settings/pages/key_activation/messages/mss_messages.tsx
index b58fe7b136..f50494df02 100644
--- a/assets/js/src/settings/pages/key_activation/messages/mss_messages.tsx
+++ b/assets/js/src/settings/pages/key_activation/messages/mss_messages.tsx
@@ -1,6 +1,7 @@
 import React from 'react';
 import MailPoet from 'mailpoet';
 import { useSelector } from 'settings/store/hooks';
+import { MssStatus } from 'settings/store/types';
 
 const ActiveMessage = () => (
   <div className="mailpoet_success mailpoet_mss_key_valid">
@@ -34,11 +35,11 @@ type Props = {
 export default function MssMessages(props: Props) {
   const { mssStatus } = useSelector('getKeyActivationState')();
   switch (mssStatus) {
-    case 'valid_mss_active':
+    case MssStatus.VALID_MSS_ACTIVE:
       return <ActiveMessage />;
-    case 'valid_mss_not_active':
+    case MssStatus.VALID_MSS_NOT_ACTIVE:
       return <MssNotActiveMessage activationCallback={props.activationCallback} />;
-    case 'invalid':
+    case MssStatus.INVALID:
       return <NotValidMessage message={props.keyMessage} />;
     default:
       return null;
diff --git a/assets/js/src/settings/pages/key_activation/messages/premium_installation_messages.tsx b/assets/js/src/settings/pages/key_activation/messages/premium_installation_messages.tsx
index b05fb8fba3..75283d854b 100644
--- a/assets/js/src/settings/pages/key_activation/messages/premium_installation_messages.tsx
+++ b/assets/js/src/settings/pages/key_activation/messages/premium_installation_messages.tsx
@@ -52,16 +52,16 @@ type Props = {
 }
 export default function PremiumInstallationMessages(props: Props) {
   switch (props.installationStatus) {
-    case 'install_installing':
+    case PremiumInstallationStatus.INSTALL_INSTALLING:
       return <InstallingMessage />;
-    case 'install_activating':
+    case PremiumInstallationStatus.INSTALL_ACTIVATING:
       return (
         <>
           <InstallingMessage />
           <ActivatingMessage />
         </>
       );
-    case 'install_done':
+    case PremiumInstallationStatus.INSTALL_DONE:
       return (
         <>
           <InstallingMessage />
@@ -69,14 +69,14 @@ export default function PremiumInstallationMessages(props: Props) {
           <DoneMessage />
         </>
       );
-    case 'install_installing_error':
+    case PremiumInstallationStatus.INSTALL_INSTALLING_ERROR:
       return (
         <>
           <InstallingMessage />
           <ErrorMessage />
         </>
       );
-    case 'install_activating_error':
+    case PremiumInstallationStatus.INSTALL_ACTIVATING_ERROR:
       return (
         <>
           <InstallingMessage />
@@ -84,16 +84,16 @@ export default function PremiumInstallationMessages(props: Props) {
           <ErrorMessage />
         </>
       );
-    case 'activate_activating':
+    case PremiumInstallationStatus.ACTIVATE_ACTIVATING:
       return <ActivatingMessage />;
-    case 'activate_done':
+    case PremiumInstallationStatus.ACTIVATE_DONE:
       return (
         <>
           <ActivatingMessage />
           <DoneMessage />
         </>
       );
-    case 'activate_error':
+    case PremiumInstallationStatus.ACTIVATE_ERROR:
       return (
         <>
           <ActivatingMessage />
diff --git a/assets/js/src/settings/pages/key_activation/messages/premium_messages.tsx b/assets/js/src/settings/pages/key_activation/messages/premium_messages.tsx
index 0e1b914897..80facf0b81 100644
--- a/assets/js/src/settings/pages/key_activation/messages/premium_messages.tsx
+++ b/assets/js/src/settings/pages/key_activation/messages/premium_messages.tsx
@@ -1,7 +1,7 @@
 import React from 'react';
 import MailPoet from 'mailpoet';
 import { useSelector } from 'settings/store/hooks/index';
-import { PremiumInstallationStatus } from 'settings/store/types';
+import { PremiumInstallationStatus, PremiumStatus } from 'settings/store/types';
 import PremiumInstallationMessages from './premium_installation_messages';
 
 const ActiveMessage = () => (
@@ -61,16 +61,16 @@ export default function PremiumMessages(props: Props) {
   const { premiumStatus: status } = useSelector('getKeyActivationState')();
   return (
     <>
-      {status === 'valid_premium_plugin_active' && <ActiveMessage />}
-      {status === 'valid_premium_plugin_not_active' && (
+      {status === PremiumStatus.VALID_PREMIUM_PLUGIN_ACTIVE && <ActiveMessage />}
+      {status === PremiumStatus.VALID_PREMIUM_PLUGIN_NOT_ACTIVE && (
         <PremiumNotActiveMessage callback={props.activationCallback} />
       )}
-      {status === 'valid_premium_plugin_not_installed' && (
+      {status === PremiumStatus.VALID_PREMIUM_PLUGIN_NOT_INSTALLED && (
         <PremiumNotInstalledMessage callback={props.installationCallback} />
       )}
-      {status === 'valid_premium_plugin_being_installed' && <InstallingMessage />}
-      {status === 'valid_premium_plugin_being_activated' && <ActivatingMessage />}
-      {status === 'invalid' && <NotValidMessage message={props.keyMessage} />}
+      {status === PremiumStatus.VALID_PREMIUM_PLUGIN_BEING_INSTALLED && <InstallingMessage />}
+      {status === PremiumStatus.VALID_PREMIUM_PLUGIN_BEING_ACTIVATED && <ActivatingMessage />}
+      {status === PremiumStatus.INVALID && <NotValidMessage message={props.keyMessage} />}
       <PremiumInstallationMessages installationStatus={props.installationStatus} />
     </>
   );
diff --git a/assets/js/src/settings/store/actions.ts b/assets/js/src/settings/store/actions.ts
index 12c0901516..0979c5d0bd 100644
--- a/assets/js/src/settings/store/actions.ts
+++ b/assets/js/src/settings/store/actions.ts
@@ -1,7 +1,9 @@
 import { select } from '@wordpress/data';
 import MailPoet from 'mailpoet';
 import { STORE_NAME } from '.';
-import { Action, KeyActivationState, MssStatus } from './types';
+import {
+  Action, KeyActivationState, MssStatus, PremiumStatus, PremiumInstallationStatus,
+} from './types';
 
 export function setSetting(path: string[], value: any): Action {
   return { type: 'SET_SETTING', path, value };
@@ -58,7 +60,7 @@ export function* verifyMssKey(key: string, activateMssIfKeyValid: boolean) {
   };
   if (!success) {
     return updateKeyActivationState({
-      mssStatus: 'invalid',
+      mssStatus: MssStatus.INVALID,
       mssMessage: error.join(' ') || null,
     });
   }
@@ -77,16 +79,16 @@ export function* verifyMssKey(key: string, activateMssIfKeyValid: boolean) {
       },
     };
     if (!call.success) {
-      fields.mssStatus = 'valid_mss_not_active';
+      fields.mssStatus = MssStatus.VALID_MSS_NOT_ACTIVE;
     } else {
       yield setSetting(['mta_group'], 'mailpoet');
       yield setSetting(['mta', 'method'], 'MailPoet');
       yield setSetting(['mta', 'mailpoet_api_key'], key);
       yield setSetting(['signup_confirmation', 'enabled'], '1');
-      fields.mssStatus = 'valid_mss_active';
+      fields.mssStatus = MssStatus.VALID_MSS_ACTIVE;
     }
   } else {
-    fields.mssStatus = 'valid_mss_not_active';
+    fields.mssStatus = MssStatus.VALID_MSS_NOT_ACTIVE;
   }
   yield updateKeyActivationState(fields);
   return fields.mssStatus;
@@ -108,7 +110,7 @@ export function* verifyPremiumKey(key: string) {
       }
     );
     return updateKeyActivationState({
-      premiumStatus: 'invalid',
+      premiumStatus: PremiumStatus.INVALID,
       premiumMessage: error.join(' ') || null,
     });
   }
@@ -133,7 +135,7 @@ export function* verifyPremiumKey(key: string) {
   }
 
   if (pluginInstalled && pluginActive) {
-    yield updateKeyActivationState({ premiumStatus: 'valid_premium_plugin_active' });
+    yield updateKeyActivationState({ premiumStatus: PremiumStatus.VALID_PREMIUM_PLUGIN_ACTIVE });
   }
 
   MailPoet.trackEvent(
@@ -148,11 +150,17 @@ export function* verifyPremiumKey(key: string) {
 }
 
 export function* activatePremiumPlugin(isAfterInstall) {
-  const doneStatus = isAfterInstall ? 'install_done' : 'activate_done';
-  const errorStatus = isAfterInstall ? 'install_activating_error' : 'activate_error';
+  const doneStatus = isAfterInstall
+    ? PremiumInstallationStatus.INSTALL_DONE
+    : PremiumInstallationStatus.ACTIVATE_DONE;
+  const errorStatus = isAfterInstall
+    ? PremiumInstallationStatus.INSTALL_ACTIVATING_ERROR
+    : PremiumInstallationStatus.ACTIVATE_ERROR;
   yield updateKeyActivationState({
-    premiumStatus: 'valid_premium_plugin_being_activated',
-    premiumInstallationStatus: isAfterInstall ? 'install_activating' : 'activate_activating',
+    premiumStatus: PremiumStatus.VALID_PREMIUM_PLUGIN_BEING_ACTIVATED,
+    premiumInstallationStatus: isAfterInstall
+      ? PremiumInstallationStatus.INSTALL_ACTIVATING
+      : PremiumInstallationStatus.ACTIVATE_ACTIVATING,
   });
   const call = yield {
     type: 'CALL_API',
@@ -169,8 +177,8 @@ export function* activatePremiumPlugin(isAfterInstall) {
 
 export function* installPremiumPlugin() {
   yield updateKeyActivationState({
-    premiumStatus: 'valid_premium_plugin_being_installed',
-    premiumInstallationStatus: 'install_installing',
+    premiumStatus: PremiumStatus.VALID_PREMIUM_PLUGIN_BEING_INSTALLED,
+    premiumInstallationStatus: PremiumInstallationStatus.INSTALL_INSTALLING,
   });
   const call = yield {
     type: 'CALL_API',
@@ -178,7 +186,9 @@ export function* installPremiumPlugin() {
     action: 'installPlugin',
   };
   if (call && !call.success) {
-    yield updateKeyActivationState({ premiumInstallationStatus: 'install_installing_error' });
+    yield updateKeyActivationState({
+      premiumInstallationStatus: PremiumInstallationStatus.INSTALL_INSTALLING_ERROR,
+    });
     return false;
   }
   return yield* activatePremiumPlugin(true);
diff --git a/assets/js/src/settings/store/create_reducer.ts b/assets/js/src/settings/store/create_reducer.ts
index 4409ee6ba9..4e9b09fa97 100644
--- a/assets/js/src/settings/store/create_reducer.ts
+++ b/assets/js/src/settings/store/create_reducer.ts
@@ -1,5 +1,7 @@
 import _ from 'lodash';
-import { State, Action, KeyActivationState } from './types';
+import {
+  State, Action, KeyActivationState, MssStatus, PremiumStatus,
+} from './types';
 
 export default function createReducer(defaultValue: State) {
   let keyActivation: KeyActivationState;
@@ -20,8 +22,8 @@ export default function createReducer(defaultValue: State) {
         keyActivation.isKeyValid = null;
         if (keyActivation.mssStatus !== null && keyActivation.premiumStatus !== null) {
           keyActivation.isKeyValid = (
-            keyActivation.mssStatus !== 'invalid'
-            || keyActivation.premiumStatus !== 'invalid'
+            keyActivation.mssStatus !== MssStatus.INVALID
+            || keyActivation.premiumStatus !== PremiumStatus.INVALID
           );
         }
         return { ...state, keyActivation };
diff --git a/assets/js/src/settings/store/make_default_state.ts b/assets/js/src/settings/store/make_default_state.ts
index 99aad33586..a450b645c4 100644
--- a/assets/js/src/settings/store/make_default_state.ts
+++ b/assets/js/src/settings/store/make_default_state.ts
@@ -19,7 +19,7 @@ export default function makeDefaultState(window: any): State {
   const mssStatus = getMssStatus(flags, data);
   let isKeyValid = null;
   if (mssStatus !== null || premiumStatus !== null) {
-    isKeyValid = mssStatus !== 'invalid' || premiumStatus !== 'invalid';
+    isKeyValid = mssStatus !== MssStatus.INVALID || premiumStatus !== PremiumStatus.INVALID;
   }
   const keyActivation = {
     mssStatus,
@@ -41,19 +41,19 @@ function getPremiumStatus(flags): PremiumStatus {
   const pluginInstalled = flags.premiumPluginInstalled;
   const pluginActive = !!MailPoet.premiumVersion;
   if (!keyValid) {
-    return 'invalid';
+    return PremiumStatus.INVALID;
   }
   if (pluginActive) {
-    return 'valid_premium_plugin_active';
+    return PremiumStatus.VALID_PREMIUM_PLUGIN_ACTIVE;
   }
   return pluginInstalled
-    ? 'valid_premium_plugin_not_active'
-    : 'valid_premium_plugin_not_installed';
+    ? PremiumStatus.VALID_PREMIUM_PLUGIN_NOT_ACTIVE
+    : PremiumStatus.VALID_PREMIUM_PLUGIN_NOT_INSTALLED;
 }
 
 function getMssStatus(flags, data): MssStatus {
   const keyValid = flags.mssKeyValid;
-  if (!keyValid) return 'invalid';
+  if (!keyValid) return MssStatus.INVALID;
   const mssActive = data.mta.method === 'MailPoet';
-  return mssActive ? 'valid_mss_active' : 'valid_mss_not_active';
+  return mssActive ? MssStatus.VALID_MSS_ACTIVE : MssStatus.VALID_MSS_NOT_ACTIVE;
 }
diff --git a/assets/js/src/settings/store/types.ts b/assets/js/src/settings/store/types.ts
index 9cfa8524dc..db4296b1dd 100644
--- a/assets/js/src/settings/store/types.ts
+++ b/assets/js/src/settings/store/types.ts
@@ -186,28 +186,31 @@ type Page = {
   }
 }
 
-export type PremiumStatus =
-  | 'invalid'
-  | 'valid_premium_plugin_not_installed'
-  | 'valid_premium_plugin_not_active'
-  | 'valid_premium_plugin_active'
-  | 'valid_premium_plugin_being_installed'
-  | 'valid_premium_plugin_being_activated'
+export enum PremiumStatus {
+  INVALID,
+  VALID_PREMIUM_PLUGIN_NOT_INSTALLED,
+  VALID_PREMIUM_PLUGIN_NOT_ACTIVE,
+  VALID_PREMIUM_PLUGIN_ACTIVE,
+  VALID_PREMIUM_PLUGIN_BEING_INSTALLED,
+  VALID_PREMIUM_PLUGIN_BEING_ACTIVATED,
+}
 
-export type MssStatus =
-  | 'invalid'
-  | 'valid_mss_not_active'
-  | 'valid_mss_active'
+export enum MssStatus {
+  INVALID,
+  VALID_MSS_NOT_ACTIVE,
+  VALID_MSS_ACTIVE,
+}
 
-export type PremiumInstallationStatus =
-  | 'install_installing'
-  | 'install_activating'
-  | 'install_done'
-  | 'install_installing_error'
-  | 'install_activating_error'
-  | 'activate_activating'
-  | 'activate_done'
-  | 'activate_error'
+export enum PremiumInstallationStatus {
+  INSTALL_INSTALLING,
+  INSTALL_ACTIVATING,
+  INSTALL_DONE,
+  INSTALL_INSTALLING_ERROR,
+  INSTALL_ACTIVATING_ERROR,
+  ACTIVATE_ACTIVATING,
+  ACTIVATE_DONE,
+  ACTIVATE_ERROR,
+}
 
 export type KeyActivationState = {
   key: string