concerning email adresses being quite easy to guess: I guess they are IF there is a rainbow table for them. Adding a salt would render currently known rainbow tables useless . . . anyway . . . that point about privacy was just a side issue that I clearly hadn’t thought through. More work/reviews needed.
Your idea (if I understand it correctly) would basically boil down to nagging my friends and colleagues to respond to my message through a channel that I impose on to them. That is in no way what I want to do. I don’t want to convert anybody.
When I start to chat to somebody, my decision on what channel to use is based upon the options that the other side is apparently using (the options that my phone book is presenting me). I want DeltaChat to be one of those options.
Or in other words:
I have one single (in numbers: 1) contact that I am currently sending DeltaChat messages to. I know that he uses it, because I myself told him about it (he is interested in that kind of stuff). Maybe there are 3 or 5 others in my phone book that use DeltaChat. But I wouldn’t know it. Because I am not comfortable “spamming” all my other 300 contacts with query messages
I understand and appreciate that DeltaChat is built upon the idea of decentralization. But looking up and finding other parties that use the same technology is something that (to my understanding) is best done centralized.