That means you don't have to use Centurylink.net webmail interface! You can check your emails using other email programs (like Mailbird, Microsoft Outlook or Mozilla Thunderbird). Using desktop email programs will make you more productive and your email will always be available, even offline.
CenturyLink Email not Working (Unable To Send, Can Not attach email on Iphone, Windows)
Optimum Email not Working -(Not Sending Email on iPhone, Mac, Windows/Android/Chrome)