LDAP with additional alias file

[JacksonYuuki]

Hi!
I spent a few hours searching for an answer to this, but couldn't find one...
I connected my dms to openldap and created some users with an additional mailAlias, which seems to have deactivated my postfix_virtual.cf file.
The setup alias list shows every alias in the file, but when I send an email to one of the aliases, I receive a bounce message saying that the user doesn't exist.

Is it possible to use both LDAP mailAlias and the addresses I defined in the file?
I want to create email distribution lists for my organisation that include some external email addresses so I can't add them to ldap.

Maybe someone here can help me or can suggest another way how I can make this work.