Error message "Not all directory objects were resolved successfully" appears when using an import (4271648)

When using an import file to populate a migration session within QMM, you may receive the error "Not all directory objects were resolved successfully". What does this mean, and how can it be fixed?

This message is due to QMM not being able to resolve at least one samaccountname in the import file.

QMM will show the objects that it could resolve, and you can use the export button to create a text file containing these items. Compare this with your original import file to determine which objects QMM could not resolve. Check the samaccountnames of these objects in the import file. Ensure that there are no mistakes and that the objects with those samaccountnames exist in the source domain. This can be done using an advanced find in Active Directory Users and Computers, for example.