Advanced Threat Protection (ATP) is ruining Outlook.com

This is now confirmed in today's announcement- https://blogs.office.com/en-us/2017/10/30/premium-outlook-com-features-now-available-to-office-365-subscribers:

For Office 365 Home and Office 365 Personal subscribers, we now offer additional security against the most sophisticated types of threats in two ways:

• Scanning attachments—Sophisticated techniques detect new types of malware previously not seen, giving you protection against today’s most advanced threats.
• Checking links—When you click a link in an email, it is checked in real-time to determine if the destination website is likely to download viruses or malware onto your computer. If the site is found to be malicious, a warning screen alerts you not to access the site.