When signing up for a new account at erpnext.com with a hotmail.com or outlook.com account, welcome/verification emails are not being delivered to the user’s inbox (or spam folder). Perhaps Microsoft is blocking emails from the domain or your server?
Have any of you tried to send an email to https://www.mail-tester.com? Our systems are self-hosted, not ERPNext.com but I was able to use this web site to identify some issues with our configuration and I thought it might help you. Good Luck.