Non-Office 365 accounts repeatedly request sign-in each time Outlook (new) is opened or restarted

If you're still having an issue with this, and the accounts in question are gmail, you can definitely add them in a way that gets rid of the repeated sign in requests every time new outlook is started, restarted, opened, etc.

It looks as though 2 factor authentication creates a problem with new outlook holding authentication. Luckily, you do not have to disable 2 factor authentication for your gmail.

Step 1 - In your account settings for new outlook, remove the problematic email/s from all devices.

Step 2 - Log into your gmail account through a web browser.

Step 3 - Navigate to "Manage Your Google Account" by clicking on your account icon in the top right corner of the page.

Step 4 - Navigate to "Security & sign-in."

Step 5 - In the search bar at the top of the Security & sign-in page, type in "app passwords" - and click the first result.

Step 6 - Enter an app name. It can be any name you want. I used outlook, since it is for outlook.

Step 7 - Click "Create."

Step 8 - Write down the password it presents you with. You will need this to enter into new outlook. You can also highlight and copy it for pasting later.

From this point, you are done with the browser/google side.

Step 9 - Open new outlook - click "Add account"

Step 10 - Enter the email address of the email you want to add - DO NOT CLICK CONTINUE

Step 11 - After you have typed the desired email in the box, look to the information under the box that says, "No account? Create an Outlook.com email account" Click that link.

Step 12 - A little window will pop up, showing and account creation page. Don't do anything here, just close it.

Step 13 - This is out bread and butter here - New buttons will have appeared on the window where you typed in your email address - Select "Advanced Setup"

Step 14 - In the "Select your email provider" list, scroll down and select IMAP.

Step 15 - Enter the app password that you just created in you google account management into the password area.

Final Step - Select continue and follow the on-screen directions.

This provides new outlook with its own direct authorization to your gmail, so the 2 factor authentication doesn't drop outlooks connection.

Classic outlook has started asking for log on of microsoft Live and hotmail accounts. None of the solutions listed have worked. On another PC I uninstalled all the accounts and reinstated them which fixed the issue but it isn't working on this one [Win 10]

1. Quick fixes
Delete and re-add the account
File → Account Settings → select the problem account → click “Delete”
Re-add the account after restarting Outlook
2. Clear Credentials Cache
Open Windows Credential Manager (control.exe /name Microsoft.CredentialManager)
Delete all credentials related to Outlook.
3. Common causes and targeted solutions
Scenario A: Outdated authentication methods
Ensure that the account uses modern authentication (OAuth2):
File → Account Settings → select the account → click “Change”
Check “Use modern authentication” (if option is available)
 Scenario B: Third-party mail service restrictions
Check if the mail provider supports OAuth2:
Gmail/Yahoo etc. need to enable “Allow insecure applications” on the web side
Enterprise mailboxes need to contact IT administrator to open API privileges
4. Registry Repair (Windows)
Force modern authentication to be enabled:
Press Win+R and type regedit
Navigate to:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity  
New DWORD value:
Name: EnableADAL
Value: 1
5. Special configuration for enterprise environment
Group Policy Adjustment:
Administrator Run gpedit.msc
Navigate to:
Computer Configuration → Administrative Templates → Microsoft Outlook 2016 → Account Settings → Accounts
Enable:
“Force use of modern authentication”
“Disable ADAL” is set to Disabled
6. Alternatives
 Use application-specific passwords (e.g. for Google accounts):
Generate a 16-digit dedicated password in the backend of your email provider
Use this password instead of the master password for Outlook logins