Having problems with a cutover migration from Exchange 2010 that I could use some help on please.
We have an organisational account in 365 with 5 users set up which were only used to get the software so are on .onmicrosoft.com email addresses. We are now looking to migrate those users and the rest of the company into 365. I've imported the domain into the account (but not changed the DNS settings yet) and set up a cutover migration from their existing Exchange 2010 server. Problem I have is that the migration failed for all users that already had a 365 .onmicrosoft account set up prior to the migration. For example one user called john.smith had a 365 account of email@example.com .com and a domain account/email address of firstname.lastname@example.org So when we ran the migration that one failed with "the name is already being used" so I deleted the .onmicrosoft user in 365 and tried again but still getting the same error. I don't understand where it is finding this name if the user has been deleted.
Would really appreciate some help with this.