Many Bulletin Board System where part of Echo Message Systems, basically how it worked was a user would post a message in a message area that was a echo. During a nightly event all echo message areas carried by that bbs system was processed and collected. Packed into a packet and routed from that system to a hub there it was processed and sent to all other systems connected to that particular echo network through out the world nightly.
So someone could write a message in Colorado and by the next morning would appear through out the United States or World usually with in 24 hours.
There where also file requests avialable and even
netmail similiar to what you would call email now.
These systems didn't require you to use a email address in the message boards so you didn't recieve "Spam" after you posted a message like in Usenet.