New Outlook App Error: "You may need an App Password"

The error

When adding or using your Rebel email address in the new Outlook for Windows, you may see:

Something went wrong. Try again. You may need an App Password.

Sometimes with a code such as INVALIDCREDENTIALS INTERACTIONREQUIRED or UNKNOWN undefined.

Despite the message, this usually isn't a password problem. If you can sign in to webmail with your email password, your account and password are working correctly.

• Plesk Hosting email: App Passwords aren't offered, and aren't needed. Your regular email password is the right one, and the message is a side effect of the Microsoft connection issue explained below.
   
• Rebel Cloud Email: App Passwords are available. If you see this message, you can try creating one by following How to create an app password (Cloud) and using it in Outlook instead of your regular password.

This guide applies to email hosted with Rebel Plesk Hosting and Rebel Cloud Email.

Why it happens

The new Outlook for Windows works differently from other email apps:

• Classic Outlook, eM Client, Thunderbird, Apple Mail and phone apps connect directly to our mail server.
   
• The new Outlook connects through Microsoft's cloud, which signs in to our mail server on your behalf and keeps a copy of your email on Microsoft's servers.

Other apps talk straight to our mail server. The new Outlook relies on Microsoft's cloud in between, and that middle step is where the sign-in can get stuck.

Sometimes Microsoft's cloud loses its connection to an existing account and can't reconnect, even though your password is correct. When that happens, the new Outlook shows the generic "App Password" message.

This is a known issue with the new Outlook and IMAP email accounts from many providers, not only Rebel. Resetting your password or changing your email settings usually won't fix it, because the connection problem is on Microsoft's side.

You can read more in Microsoft's community forum: Existing IMAP accounts inaccessible via New Outlook.

What we've confirmed

We've investigated this issue in detail, including testing with Plesk and raising it in Microsoft's community forum:

• Your password works: the same email and password sign in successfully to webmail, Classic Outlook, eM Client, Thunderbird, Apple Mail and phone apps.
   
• New accounts are added normally: a brand-new mailbox on the same domain and server can be added to the new Outlook without errors. The problem affects existing accounts that Microsoft's cloud has already connected to.
   
• Other providers see the same thing: independent email providers have reported the same behaviour with the new Outlook.

Common questions

Do I need to create an App Password? For Plesk Hosting email, no: App Passwords aren't offered or needed, and your regular email password is the right one. For Rebel Cloud Email, you can create one, and it's worth trying if you see this message.

Will resetting my password fix it? Usually not. Your password isn't the cause, so changing it often doesn't help the new Outlook reconnect.

Can Rebel fix this on our servers? The connection that gets stuck is between Microsoft's cloud and our server, and only Microsoft can reset it on their side. Our servers are working normally, which is why other apps connect without any issues.

Is my email safe? Yes. The emails on our mail server aren't affected when the new Outlook can't connect, and you can see them in webmail or another email app. If your account was set up as POP, some older messages may be saved only on your computer: see the POP section below before making changes.

Can I keep using the new Outlook? If your account is already in the new Outlook and only some emails aren't syncing, check your account's server settings in Outlook against the table in Fix 2. Please don't remove the account and add it again: if Microsoft's cloud is stuck, you may not be able to add it back. For reliable access, we recommend Classic Outlook or one of the other options below.

Fix 1: Use Classic Outlook (recommended)

Many people were switched to the new Outlook by a Windows or Office update without realizing. Classic Outlook connects directly to our mail server and isn't affected.

To switch back:

1. In the new Outlook, turn off the New Outlook switch at the top right, or go to Help > Go to Classic Outlook.
    
2. If Classic Outlook doesn't open, click the Start menu and search for "Outlook (classic)". It's included with most Microsoft Office and Microsoft 365 installations.

If your email account isn't already in Classic Outlook, add it manually:

1. Add a new account, choose Advanced options, tick Let me set up my account manually, and select IMAP.
    
2. Enter the settings from the table in Fix 2 below.

Fix 2: Use another email app

If you don't have Classic Outlook, or would like something different, these apps also connect directly to our mail server:

• eM Client (emclient.com): free for up to two accounts, and looks and works much like Outlook. It includes a built-in tool to import your contacts and calendar from Outlook.
   
• Mozilla Thunderbird (thunderbird.net): free, and handy for managing several mailboxes.
   
• Webmail: always available in your web browser, with no setup needed.

Your email settings

Always choose IMAP, so your folders stay in sync across your devices.

Replace yourdomain.com with your own domain name.

If your emails are saved on your computer (POP)

If your email was previously set up as POP, some of your older messages may be stored only on your computer, not on our server. Before removing or changing the account in Outlook, save a copy so nothing is lost:

1. Export your emails, contacts and calendar to an Outlook data file (.pst) by following Microsoft's guide: Export emails, contacts, and calendar items to Outlook using a .pst file.
    
2. Set up your account again using IMAP.
    
3. Import the .pst file into Classic Outlook or eM Client, if you'd like those messages back in your mailbox.

If you're unsure whether your account uses POP or IMAP, contact us and we'll check for you.

Still having trouble?

Contact our support team by Live Chat or by email, and include:

• The email address you're trying to use
• Which app and version you're using (new Outlook, Classic Outlook, eM Client, or another app)
• Whether you can sign in to webmail with the same password
• A screenshot of the error

With those details, we can confirm your account is working on our side and help you get connected.