then maybe they are sending the email out in batches? they have checked a batch of applications that ll required documents are present and this email out. Maybe they will send it out to more applicants as their application materials are checked against the required checklist.
then maybe they are just sending it in batches
they must have checked a batch of applicatons that they have all materials as required in the checklist and sent this email out
maybe they will send out the email to other applicants as they check more applications