diff --git a/src/apps.js b/src/apps.js
index 2f23cdb55..3cab65020 100644
--- a/src/apps.js
+++ b/src/apps.js
@@ -1484,7 +1484,9 @@ async function setMailbox(app, data, auditSource) {
     let error = checkAppState(app, exports.ISTATE_PENDING_RECREATE_CONTAINER);
     if (error) throw error;
 
-    if (!app.manifest.addons?.sendmail) throw new BoxError(BoxError.BAD_FIELD, 'App does not use mail addons');
+    if (!app.manifest.addons?.sendmail) throw new BoxError(BoxError.BAD_FIELD, 'App does not use sendmail');
+    const optional = 'optional' in app.manifest.addons.sendmail ? app.manifest.addons.sendmail.optional : false;
+    if (!optional && !enable) throw new BoxError(BoxError.BAD_FIELD, 'App requires sendmail to be enabled');
 
     await mail.getDomain(mailboxDomain); // check if domain exists