Why could exchange 2016 and exchange online mailboxes be duplicated?

Question

Microsoft Exchange

Colleagues, good day! Faced such a situation. When I came to the organization, office365 was connected, but the mail works on the local server. However, in Exchange Online, 10 employees' mails appeared in the recipients (more than 140 employees in total, Azure AD is synchronized). and so for these 10 mails, in fact, all letters come and are stored on a local server, but if you connect to them through Outlook, you get office365 settings and get into cloud mail, which, of course, does not contain letters. The question is how to migrate these 10 mails? When I create a batch of migration - these users are not in the list. With migration of other boxes of problems is not present. But what to do with these boxes? I cannot delete mailboxes in Exchange Online. Users cannot be deleted. How these boxes got there, I don't know. Several new ones appeared in this list already with me when creating new mails. At the same time, hybrid migration was not configured (I did this myself a few days ago)

Answer 1

Check the SMTP addresses of these users. Compare them to those who do not have such problems. Most likely, this is a cant with addresses [email protected]