Unable to log in to Plesk 360:
You are trying to log in to an account that has not yet been verified. Check your inbox for an email with a verification link. Follow the link to verify your account and log in. Then you can start managing your licenses in Plesk 360.
The recipient mail is being hosted on Office 365. The verification email has not been received (even in Spam)
Office 365 detects and places emails to quarantine.
Find and release messages that were quarantined instead of being delivered.
To check the quarantined messages:
Go to the quarantine page at https://security.microsoft.com/quarantine?viewid=Email
Note: It will be needed to sign in using Office 365 credentials (user ID and password)
On the page, there will be a list of any messages that were received, but were redirected to the quarantine due to the policy specified.
Select the necessary quarantined message to view details about it, and take actions
Note: If the message wasn't actually spam, it is possible to release it (have it sent to the mailbox) and report it as not junk to the Microsoft Spam Analysis Team.