If you have organized group you can probably use methods like codebook with Huffman coding to reduce message length a lot. Plain text is very sparse form of communication, compared to good codebook which suits the needs. Btw. This is over 20 years old stuff. MUDs in very early 90s were used for all kind of communication. - Nuff said. Also utilizing chaffing and winnowing allows you to use almost any kind of service to transfer your data. You'll just hide it in the junk. Only receiver will know what's meaningful and what's not.