[wongarsu]

> The data going into each "mailbox" either needs to be immutable, or deep copied to be thread safe

Or moved. The mailbox/process pattern works great in Rust because you can simply move ownership of a value. Kind of like if in C you send the pointer and then delete your copy.

Of course doing this across threads doesn't work with every type of value (what Rust's type system encodes as a value being `Send`). For example you can't send a reference-counted value if the reference counter isn't thread-safe. But that's rarely an issue and easily solved with a good type system.