A user reports a workstation has been performing strangely after a suspicious email was opened...

https://partners.comptia.org/docs/default-source/resources/comptia-a-220-1102-exam-objectives-(3-0)

When a user reports that their workstation is behaving strangely after opening a suspicious email, the first step a technician should take is to run a virus scan on the computer. This is because opening a suspicious email is a common way for viruses and malware to infect a computer. Running a virus scan can help identify and remove any infections that may be causing the computer to behave strangely.