How to get a backup of Office 365 accounts?

I have 5 Office 365 cloud accounts. I want to close 2 of them, but before this, I want to back up my important Office 365 account emails. I went through the manual solutions but found them difficult. Is there anyone who can suggest me a simple and quick solution to backup Office 365 emails?

Please read a complete guide here https://docs.microsoft.com/en-us/exchange/back-up-email