Incomplete submissions turn into long email threads because the vendor usually finds out what is missing one item at a time, often after a reviewer has opened the file and written back. Each round adds days, and the thread becomes the only record of what was asked for.
The better setup is to check the submission as soon as it arrives and give the vendor a complete list of what is missing or not acceptable in one go, ideally through a portal where they can see the status of every requirement. That replaces the email chain with one clear view for both sides of what is done and what is still outstanding.