Amie: Write in code?
"Uhh… write in code?" suggests Amie.
"Aha! Very clever. But codes can be cracked, especially if your enemy has a whole lot of time on their hands, and remember, you are very paranoid, and you're playing for all the marbles. Can you risk it? Better not. There's a safer way, gotta be. So what do you do?"
Another possibility: Hide the real message behind the words. Literally, in this case.
"Hide your mail!" says Lia, who thinks she's figured out what Bina is up to. "You could use a dead drop."
"Very good, person whose name I can't remember," says Bina. "But what if your enemy knows the environment better than you do? You can't be sure your dead drop will stay secure. So what do you do?"
Amie and Lia, for reasons that, if asked, they would not be able to fully articulate, look at Wong.
"You have to offer a suggestion." says Lia.
Use the telephone instead?
"Fine! You… I dunno, you use a telephone instead? Why am I involved in this!?"
"Yes!" says Bina. "Or, to be more precise, no, but close! Very close. You simply stop writing things down."