Hi Welcome to JustAnswer.com I am Tech Specialist and today, I will be trying my best to solve your issue.
Advantage is it's a fast/secure way of delivering messages
You can send big files via email
The biggest advantage is it's free/cheap
There is no such disadvantage of using emails but one can be this: if any user does not have much tech knowledge or an email address, you can't send mails to them. Also, personally written mails/bills can be send only via postal mail and not emails.