In Australia, we know that email-based attacks are the most common Cyber Security threat.
While doing some research for my own knowledge, I found this great article on a USA government website (Cyber Security Infrastructure Security Agency www.cisa.gov) titled: "ACTIONS TO COUNTER EMAIL-BASED ATTACKS ON ELECTIONRELATED ENTITIES"
This PDF article is focused on US Government Agencies but the advice would also apply to businesses in Australia.
There are some good detailed tips for System Admins to take note of. Enjoy!