If e-mails are available online, then you have connection between your e-mail account and the e-mail server and you can access your mailbox via this connection. This ensures that you have access to the latest e-mails in your mailboxes.
As the e-mail is managed on the e-mail server, it is not a CAS genesisWorld data record. You manage e-mails on an e-mail server, for example, via the E-mail Client in CAS genesisWorld.