Bitmessage is a really cool project because it relies on PoW (proof-of-work) to send messages. Hence for spammers to flood the network would require lots of com

Bitmessage is a really cool project because it relies on PoW (proof-of-work) to send messages. Hence for spammers to flood the network would require lots of computing power. This means that the network should be full of healthy messages that should be human written. You don't need complex social trusted networks (like scuttlebutt does) to just enter the network and start relaying messages around - you trust they're not spam since there's PoW behind them. However the PoW requirement when I last used this was quite low hence spam was somewhat still present. I'm also not sure how long a message is kept around the network: say I enter the network and send a message to Alice; how long will the message be kept alive in the network by peers so that Alice can still read it when she joins? Edit: I guess my last concern is simply validated by the fact that the sender can just enter the network again and resend it. From paper: >. If the sender of a message did not receive an acknowledgement and wishes to rebroadcast his message, he must update the time and recompute the proof‐of‐work.