During the Merge/Provision process, the following errors may be returned:
ERROR: [7436-1-98-00000000] Unable to merge object. Reason: 'CN=Test,OU=NOTES-Contacts,OU=Messaging,OU=Test,OU=OU,DC=MS,DC=DC, DC=com'
'CN=Test,CN=Users,DC=ms,DC=dc,DC=com' is mailbox-enabled.
ERROR: [7559-1-221-00000000]
AdFwd::_PSHEnableObject() - PowerShell Result: ErrorId: 81C654BB
Error: The proxy address "SMTP:TEST1@CS-CP.COM" is already being used by "CS-CP.COM/Users/Test". Please choose another proxy address.
This indicates that the user object you're trying to merge the contact object with is already mailbox enabled.
Either remove the mailbox or offending proxy address from the user object and merge again or move on to another user which does not already have a mailbox.