You can update an email source definition to reflect folders or precision for the fields in the source definition. You can update a source definition in the following ways:
Reimport the definition. If the changes are significant, you can reimport the definition. This overwrites or renames the existing source definition. You can retain existing descriptions in the source definition being replaced.
Edit the definition. Manually edit the definition to configure properties that you cannot import or to make minor changes to the definition.