“If you’re not paying for it, then you are the product”
Technically, there is no such thing as a free email account. Email accounts must be paid for somehow, either by advertising or collecting your data. But having said that, free email addresses are very useful.
You may wish to have a back up email account, just in case something happens to your main email account, or you may wish to have an email account independent of your broadband (ISP) provider.
Free to use
Gmail
provided by Google. Gmail offers a mail import from other email. To sign up for Gmail you will need to create a Google account
https://accounts.google.com/signup/v2/webcreateaccount?flowName=GlifWebSignIn&flowEntry=SignUp
Hotmail/Outlook
provided by Microsoft. You will need to create a Microsoft account.
iCloud
provided by Apple, great for Apple fans. You will need to create an Apple ID
https://support.apple.com/en-gb/HT204316
Free (with lots of adverts) but with a paid for version (No Ads)
Yahoo Mail (Ad free – £26.99 a year)
https://login.yahoo.com/account/create?specId=yidReg
Further reading
https://en.wikipedia.org/wiki/Comparison_of_webmail_providers
How long do free email providers keep your account alive?
https://mashable.com/2009/02/09/webmail-account-dormant-alive/?europe=true