Are you sure now you are not mixing the password and the PIN? I checked my previous post and the information told in it is both accurate and valid.
To put it very short: if you sign in to windows using an MS account
Email1@
OutlookOrHotmailOrLive.com, and you want to add
Email2@
OutlookOrHotmailOrLive.com to the Mail app, the PIN asked is the PIN (not the password) for the
Email1@
OutlookOrHotmailOrLive.com, your current Windows sign-in account.
Below a live example with screenshots.
By default a Windows user account has no PIN. It needs to be set up, either when installing Windows or later on if skipped when installing. When set, the PIN for the Windows 10 sign-in is four or more digits long, as the user prefers. In your case if it auto enters after 4 digits, you have a 4 digit PIN. I use a 5 digit PIN, in my case when I add a new Microsoft email account to mail app it auto enters after the 5th digit.
Here's how it works:
My Windows sign-in MS account
kari@abcdefgh.com is already automatically added to Mail app, later on I have added a second MS account. Now adding a new account
larry.laffer@abcdefgh.com, I enter this new account's credentials normally:
When added, the account tells
Attention Required. Clicking the account I get the option
Fix account selecting it:
The next dialog is a bit confusing. It asks me to verify that the
larry.laffer@abcdefgh.com is mine by asking the current Windows 10 sign-in accounts PIN, that of
kari@abcdefgh.com
I enter my Windows sign-in 5 digit PIN for the user account
kari@abcdefgh.com, the account I am currently using to sign in to Windows, and now the
larry.laffer@abcdefgh.com will finally be added to the mail app.
If you are not sure which PIN you have set up, if you have forgot it, go to your account settings and change it. Notice that if you have forgotten the PIN, you need first to remove it, then set a new one. Changing the PIN will first ask the old PIN which of course if you have forgotten it you cannot enter.
Kari