Listservs are essentially forums for discussion (e-mail discussion groups managed by LISTSERV, MAJORDOMO or other software) which enable communication between individuals with shared interests, professional concerns, etc.
Listservs have two addresses: one for public postings; another for subscribing, unsubscribing, or cancelling mail while on holiday, etc. The non-public address will always be to a listserv.
To subscribe to a listserv:
You will automatically receive confirmation of your subscription, and information regarding posting messages, unsubscribing, etc.
National Archival Listservs
Provincial Archival Listservs
International Archival Listservs