Supposed to be. Email these days is also instant and I have indeed people calling right after sending emailing to ask if I got it. I never did or will use outlook , but I know many people in business settings who use the slowness of it (‘stuck in outbox’ etc) to force it to be more async. With gmail or others you don’t have any excuses; it’s as fast as chat.

If people who send a chat message are all asking me ‘if I have time to talk’, life is over if I say yes; it is always no aka async. And for most people I work with and definitely friends, that works well, just strangers usually have to be educated a bit and some never learn (and are just ignored generally).