Mail Filter "Has not been previously delivered"

I cannot find any info on the following filters anywhere. "Has not been previously delivered" and 'is an error message." Have googled, cpanel forums, and exim documentation. Are they custom filter added by my webhost or just new ones?

Either way can someone explain them fully. Like 'is an error message', does that mean all message from postmaster?

"Has not been previously delivered", maybe checks a file of previously filtered mails and won't send to repeat recipients(one mail per unique sender)? of maybe checked the header to see if it is a response to a mail forwarded due to a previous filter?

 

I see just different wording is why no searches came up. Thanks for the help.