Duplicate proxyAddresses error and soft-deleted users in Azure AD

[Gurdev Singh]

Could the values of UPN and proxyAddresses of soft-deleted users in Azure AD cause duplicate proxyAddress attribute synchronisation error?

E.g., if a guest user exists with email address of bob@contoso.com in Azure AD and we soft-delete this guest account. Once guest is soft-deleted, we do a domain migration and create a member type account in on-premises AD for bob with username and email of bob@contoso.com. Will AAD Connect have any issue in synchronisation given the old guest account still exists albeit in soft-deleted state. 

[#2]

IIRC, it will ignore any soft-deleted entries. In any case, if that's a Guest user object, usually you can delete it without any complications.

[#3]

Thanks Vasil...What does IIRC stands for?

We are doing a domain migration where source users already have guest accounts in target tenant. In order for source users to have same UPN and email in target their guest accounts will be soft-deleted given guests will have same emails. Only reason we won't permanently delete these guest accounts is in case we had to back out.

[#4]

IIRC = If I recall correctly. In other words I was too lazy to verify the behavior before replying here :)

[#5]

If the guests are already exists in the tenant - you can also consider this scenario of converting guest user type as members and perform matching between cloud identity and on-premises identity.