When I run ldapsearch from the command line I can find everything I want… still, Zammad does not find them when I go to the “Users” section nor when I want to send an email in a trigger.
as you said that the search filter does return all users you’re expecting with a ldapbrowser, the filter should™ be fine.
So everything that’s in theory left is something being up with either the account (e.g. duplicate unique identifier aka email or the account identifier being detected incorrectly).
Zammad checks the first entries during setting up ldap and then anticipates the correct UUID identifer.
For Active Directories this should be samaccountname. OpenLDAP usually uses uid.
That depends on your LDAP source.
In rare cases or maybe even unclear situations Zammad may guess wrong and pick an identifier that’s invalid. This means e.g. samaccountname seemed correct but uid would have been. In those situations above described issue may appear. The UID field may not be empty.
You can check within the integrations page (for the identifier part) and double tab that Zammad guessed correct.