I created a user some time ago called “nicola”
Note that I use the standard kopano user creation i.e. no LDAP or anything else, just plain kopano.
After a while I deleted the user with
kopano-admin -d nicola
I also purged all messages with:
When I send an email to “everyone” I stil get a failed delivery note saying that the user “nicola” does not exist.
Kopano core version: latest production from the supported website.