There are many places on line for correspondence on favorite subjects. CompuServe, America Online, and Prodigy have forums for thousands of interests. Any message posted is immediately available for others of like interest to read and answer. CompuServe has a well-developed collectibles forum of limited interest to antiquers. Antiques areas on America Online are scattered and hard to find.
Mailing lists are easiest to use.
Every time you log on to get your E-mail, you also get all the messages from the mailing lists to which you subscribe. Any comment or reply sent to the mailing list administrative site is automatically copied and sent to all other subscribers. Subscription is usually free. There is no central list of mailing lists, so finding ones suiting your interests is sometimes difficult. Usenet newsgroups work more like CompuServe forums.