Dunning letter on Invoice hold, dispute invoice and dept status on invoice

Dear Team,

I have the following clarifications regarding Dunning letter generation:

a. When an invoice is in dispute or marked as debt, how does the system treat these invoices during Dunning letter generation? By default, will the system pick them up and send the Dunning letter to the customer, or will they be placed on hold for a certain period? Is there any setup option available to include or exclude such invoices?

Kindly advise what the standard practice is in Advanced Collections.

b. If there is no primary email ID defined for the customer, will the system still send the Dunning letter?