Google domains registrar provides a free service to forward up to 100 e-mails from the custom domains. To enable this service navigate to Email tab in the Google Domains Console.

Specify the e-mail to forward from the in the first box and e-mail to forward to in the second box.

Add new E-Mail forwarding
Add new E-Mail forwarding

verification code will be sent to the destination e-mail. Until the e-mail is verified the forwarding is not enabled:

Pending for e-Mail forwarding verification
Pending for e-Mail forwarding verification

Once e-mail is verified the warning is removed:

Validated E-Mail forwarding record
Validated E-Mail forwarding record

Unlike forwarding with GoDaddy, Google Domains enables the encryption for the forwarded e-mails:

Received e-mail with encryption
Received e-mail with encryption