What is the default number of hours for a mail to get bounced back?
The default for bouncing email is 24 hours. This is a RFC standard, and I do not know where or if it could be changed. If people are truly worried about mail arriving, they should use delivery confirmations and return receipts. This will work better for Notes internal routing, as most SMTP servers automatically strip out return receipts.
This was first published in April 2003