You first need to ensure that you have set up your email accounts in the Helm control panel before you try to connect with your username and password. You will set up both a username and a password there, which you will use later to connect to your mail account.
Once you have created your mail account in Helm, you will need to enter this information into your mail client such as Outlook Express, Netscape, etc. Your username and password will be the same email username and password you set up for that user account in Helm. Remember to enter the username in the format username@yourdomain.com where yourdomain.com is the name of your website domain.
