On Thu, 28 Oct 2021 at 00:15, <dovecot@ptld.com> wrote:

[...]

> I think my "creating users" was me wanting to make sure that when
> postfix
> passes an email for "barbaz@mydomain.com" to Dovecot, then Dovecot will
> store it and wait for
> someone to come along and impersonate barbaz. i.e. "barbaz" doesn't
> have to exist as a user
> already before Dovecot will store the mail.

If you are using LMTP dovecot will only accept emails from postfix that
it can lookup the /directory/path to from one of the userdb{} or
passdb{} sections. If dovecot can not find a match in any of the
userdb{} or passdb{} it will reject the email as user unknown causing
postfix to send a undeliverable notice email back to the envelope sender
address, also known as back-scatter. I am not aware of a way to use
wildcard addresses in dovecot userdb{}, i don't think its possible but i
don't know what i don't know.

So I think this will be the main issue now - there's no way of knowing the 

addresses ahead of time, so it sounds like I'll need to add them to userdb{} when they

hit postfix and before they get passed to dovecot.