Welcome to Atomnet
From here, you can access Atomnet Electronic Mail. Alternatively, you can configure a desktop mail client, such as Thunderbird, to read your mail.
If you're not using a secure connection already, it's worth taking a moment to change that. A secure connection encrypts your mail between your computer and the server and protects it from prying eyes. Open your mail preferences and check anything marked 'Use secure connection' or 'Use SSL'. If you send mail through mail.atom.net, you can enable a secure connection for that, too. Here, the option you want is 'Use TLS'.
You may need to download the certificate to ensure that your software will recognize the server.