Is it illegal to change the mailing address of a deceased person?

On death all relationships would be terminated, so a deceased person should not be getting any mail - all relevant parties - government authorities, pension providers, utility and finance organisations etc should be notified.

There might however be correspondence arriving from the fact of the death, those items should the addressed to 'the estate of' the deceased or the person winding up the estate (in his or her own name).

A court appointed executor or administrator would have the authority to submit a change of address at the post office to redirect mail to the fiduciary who is in charge of settling the estate especially if the fiduciary resides at some distance from the decedent.