questions and Answers1:A source email address couldnt be found in the on-premises domainUnhide the user from the Exchange server's Global Address List and perform the Migration.2:This mailbox exceeded the maximum number of large items that were specified for this request. --> MapiExceptionMaxSubmissionExceeded: IExchangeFastTransferEx.TransferBuffer failed (hr=0x80004005, ec=1242)"This error is commonly seen if the user's mailbox contains one or more email items that exceed the 35-megabyte (MB) message limit. 2.Using outlook change the View to List. Arrange all items in all folders of the user's mailbox by size. Sort the items from largest to smallest so that the largest items are at the top of the list.3.Locate the largest Item larger than 35 MB. Depending on how important email item is, you can export into pst or shift delete from user mailbox and then proceed with migration.3:A different type of Active Directory object already exists for user@domain.com in the target forest. Please verify that the SMTP address is correct"a.Log on to Office 365 Portal and Navigate to Users and Groups.b.Search for User which Failed to Migratec.Delete the User Object permanently Using GUI or Exchange PowerShell using command let below (Imp : If you have configured onedrive or contain any sharepoint data for the user , ensure you take a back up prior removing the object)Remove-MsolUser -UserPrincipalName User@Domain.com-RemoveFromRecycleBind.Ensure User is Successfully Removed from User and Groups In the Portale.Perform the Cut over migration.for Domino to office 365 mIgration. This has to be done in the source 1:create a txt file for the UPNrun the command from the powershellgc file.txt | get-recipient | group recipienttypedetailsthis command will tell us if all the users are with mailboxs in the Souce or mailenable users.