Hello O P,
Based on discussions and technical sources, here are some possible reasons:
Possible Causes
- Strict security policies for certain regions by Microsoft services, especially when the system detects “unusual sign-in behavior”;
- Suspicious activity flags might be triggered by Brazilian IP addresses, even if nothing illegal is happening;
- VPNs causing sign-in issues or account locks, which has been observed by other Outlook users;
- Some users reported email delivery problems caused by routing through Brazilian server nodes.
Suggested Fixes
- Add a trusted device: Log into your Microsoft Account Security page and mark your current device as trusted.
- Enable two-factor authentication: Use Microsoft Authenticator or SMS to boost account credibility.
- Update your account security info: Add a phone number and backup email to reduce the chance of false flags.
- Avoid unstable networks or frequent IP changes: Try to stick to a reliable home connection.
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Best regards,
Ami | Microsoft Community Support Specialist