Reject is simple managed reject messages.
Sometime you get annoying messages from someone, store, ads or even our network provider.
You want simply remove it but sometime you do not want remove it entirely. Because may be once they have useful information, but most of them not.
Simple managed reject, you can reject by recognise the sender, put it into Reject List - automatically Reject app will filter them for you.
Those reject messages will be saved in specific time, default in a week (you can configure it at setting), otherwise the reject messages is going to be deleted.