Sites connected with actual mailing lists dealing with computers in general.
Sites for mailing lists which focus on a specific part of computing (for example: security, Apple Macs, graphics software, or web design), or indeed any non-computing topics, are generally listed under the category for that topic (in a mailing lists sub-category should one exist).

(See also Computers: Internet: E-mail: Mailing_Lists: By Topic)

Sites dealing with mailing list software and hosting services are listed under Computers: Internet: E-mail: Mailing_Lists