UPDATE: This issue was resolved with Aid4Mail version 5.0.16. You can upgrade your version of Aid4Mail 5 by clicking here.
Currently if you use our alternate engine (“Process using Outlook (recommended) turned-off/unchecked” to process to a PST file that already exists and you want to append emails to the PST file, you will receive an error message.
If you use Outlook (as recommended), it can append emails to an existing PST file.