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It showed up in my Hotmail account which is from years ago which now opens in the window as oulook.live.com in my chrome browser.
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Webmail through Chrome is a "nothing to do"
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I have Outlook (V2408 Build 17928.20114) installed on my laptop. I have set it up to receive emails from 3 ISP's including bigpond and iinet. All are POP/SMTP.
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Nothing to do
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I have a gmail account as well. On my laptop it is open in my chrome browser and on my iPhone I use the gmail app.
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Nothing to do.
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My default Mail App is iPhone Mail app. I set it up to bring emails from my Hotmail, iinet and Bigpond accounts.
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For Apple Mail, you many need to remove and replace your Hotmail/Outlook.com account;
If you use Apple Mail:
Apple Mail supports Modern Authentication by default when you setup the account as Outlook.com. If you use Apple Mail and you are seeing password prompts or connection errors, this is most likely happening because your account got configured as basic authentication. To mitigate the issue, remove the account and add it back as Outlook.com:
- Go to Settings> Mail> Accounts.
- Tap the email account you want to remove from your iPhone, then tap Delete Account. For more information, please go to Add and remove email accounts on iPhone.
Add your account back to Apple Mail:
- Go to Settings > Mail.
- Tap Accounts, then tap Add Account.
- In the Add Account dialog, choose Outlook.com.

If removing and re-adding the account does not address the issue, do the following:
- Remove the account again.
- Go to Settings> Safari, then tap Clear History and Website Data.
- Reboot your iPhone.
- Add the account back and proceed through the Outlook.com account sign in flow.
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Back to hotmail/outlook.live in my chrome browser - I just noticed under the menu bar a message saying "Avoid losing access to Outlook by adding a recovery phone number"
Is that a simple solution to the issue?
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This has nothing to do with the issue. It is a very important account recovery step and definitely should be done. MFA is coming and you can't have too many second factors.
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Every month Microsoft sends me an email with my Microsoft 365 Apps for business invoice. It is sent to my bigpond a/c.
When I click on the link to View your invoice it takes me to a pop-up window "Action Required. Security defaults are enabled to keep your organization secure. Follow the prompts to set up a multifactor authentication method to protect your account."
The window has my onmicrosoft.com email address.
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Like I said MFA is coming. The message is in reference to your onmicrosoft account which will soon require MFA. That is the address It wants you to deal with. The Authenticator app is a valuable "second factor" as are phone numbers and different email accounts. The more, the merrier. The Authenticator app can be used for your onmicrisift account, your Hotmail account, and many others. I have it on my phone and find it highly useful.
FWIW, we're discussing two different issues, Authorization and Authentication. Authentication is an MFA kind of thing and that's not the real issue with the email change. Email is switching to OAUTH2, which is Authorization in nature. For example, Authentication gets you into your Google user account, Authorization is what gets you into your Gmail mailbox after you've Authenticated. Authorization is the change Microsoft is making to Hotmail/Live mail/Outlook.com