how to handle email after an employee's departure

When an employee chooses to leave or is asked to depart an organization, there are five main options that most organizations choose from:

1) the email address is directly forwarded to another staff member who will sort through it and forward personal emails to the departed employee

2) We put up an autoreply that says “for company related items, email 'this staff member' at this address, for personal related items, email the former employee at this address”

3) A combination of 1 and 2 where we forward all emails to another staff member and we put up an autoreply that essentially says "this employee has left the organization, but your email has been forwarded to [name], who will handle your email appropriately"

4) We allow a non-departing staff member to open the departed employee's mailbox as an extra mailbox where the non-departing staff member can view the departed employee's emails in an inbox separate from his/her own.  This can be used with or without an autoreply on the departed employee's mailbox.

5) We delete the former employee’s address so people get a bounceback when they email that address