I never used CompuServe forums but my understanding is that they were public internet forums, not exactly something that could be used for personal/private mess

I never used CompuServe forums but my understanding is that they were public internet forums, not exactly something that could be used for personal/private messaging. Newsgroups (often used with an email client) pre-dated CompuServe forums by a decade and I'm pretty sure they had a much larger user-base. AOL Instant Messenger didn't come out until 1997, email was already in heavy use by then.