An odd one I know, and definitely would need to be configuration option rather than the default behaviour, but would it be possible to stop Totara requiring that an email address is unique?
Example: We have a number of users who we don't currently have a valid email address for, so we need to use a generic account and then track them down as they use the system to obtain a valid email address. Currently we have been able to use Totara Sync to set the same email address for all of the accounts, but we can't set individual accounts to use the generic email account.
Example 2: We have some users who need two accounts due to the way our organisation is structured, so both accounts should have the same email address.
As I say, not the normal behaviour but it would be helpful in certain cases.
Dan