What account type are you adding to Outlook (POP/IMAP/Exchange)?
Has Microsoft made any changes to the smtp settings?
Microsoft haven't made any recent changes to your SMTP settings. For outlook.com accounts, you can still use smtp.office365.com to send email from devices and applications. For other account types, depending on your email provider.
Is using an app password a requirement if using third party apps?
It also depends on your email provider. As far as I know, for example, if you want to configure your Gmail account as a POP type, you can use an app password. More information, please see: Sign in with app passwords - Google Account Help.
Hope this helps!
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