issues with email hacking?

issues with email hacking?

Started noticing last night that my zoho email was sending tons of "mailer-daemons" back to my email, for something I didn't send.
  1. Is it easy for people to hack the zoho email?
  2. Am I at risk whenever I check email, even if by phone, even if I have my password saved rather than having to put it in each time? 
  3. For this time, do I just need to change my password?