Improve password emails on sandboxes

Currently when a new sandbox is created it emails admins that are added that their password is expiring even if the security policy on the originating instance does not require this (it looks like this is because they are migrated with the existing password, but with an expiration). The emails look like a phishing attempt given the random url that is generated. It would be ideal to explain in the email why they are receiving it or an option to suppress them as every time we generate a new sandbox it causes internal confusion. Thanks for considering some improvements here!