Recently I've created a sharepoint page and I shared it with other people who don't have an account in my domain, but they have account in other Microsoft Exchange domain. When they want to login to the page first time, some of them don't have email address assigned to a new account. So in "Admin center" I see guest accounts and some of them have email addresses assigned and some don't have. More explanations in the attachment.
I don't know if the problem is with synchronisation between microsoft services or with something else. How to add email addresses (eg. using powershell)?
Users without email addresses have problem with login to the sharepoint service, but I find a solution and I put an email address for these users in sharepoint manually.