If you wish to use a custom URL for your email address, and either do not want to use the email hosting provided by your domain registrar or email hosting is not provided, you have a couple of options.
Regardless of the option that you choose, you will need to create an MX record in your DNS settings similar to how you created a CNAME record for the custom domain. You'll need to follow the instructions provided by the email host to create the appropriate MX record in your DNS settings.
Zoho Mail provides 5GBs of mail storage on their free plan. Most users will need a single email account, but the free plan with Zoho allows for you to register up to 5 accounts.
Google Business Apps offers 30GB of mail storage per account at $5 per month per account.