Depending on your software you may be able to automate this, e.g. for mails over a certain age to be deleted. Read the help for you software for details. There are a number of services that are available via email. The commonest use of email. Mailing lists are organised for discussion round a single topic.
Topics range from rock band fan clubs, to self-help groups for all sorts of medical conditions.
Mailing lists usually have two mail addresses, one you use to join and leave the list, and one you send actual posts for the list to. When you join a list you will normally be sent a lengthy message describing How to leave the list. What the do's and don't of the list are. Often a list will have a charter and you should stick to this. When you post mail to the list a copy is forwarded to all recipients of the list.