Yahoo! Groups operate as both electronic mailing lists and Internet forums. Group messages can be posted and read by e-mail or on the Group homepage, like a web forum. Members can choose whether to receive individual e-mails or daily digest e-mails, or to read the posts at the web site. Some Groups are simply announcement lists, to which only the Group moderators can post, while others are discussion lists.
As well as providing e-mail relaying and archiving facilities for the many lists it hosts, the Yahoo! Groups service provides additional functions on the web site, such as voting and calendar systems and file uploading. The basic mailing list functionality is available to any e-mail address, but a Yahoo! ID is required for access to other features.