There are 2 main options for this:

You can use the webmail software which means you can access your email anywhere using your browser:
www.yourdomain.com/webmail/

Secondly, you could setup your email client to use IMAP.

IMAP means that your client will not download and remove messages from the server. It will leave the messages on the server so you can view them from multiple locations. The downside is that you need to be connected to the internet to view your messages.

Set your client up to use IMAP and use mail.yourdomain.com as the server.