If you don't import the users from NemID medarbejdersignatur when connecting to MitID Erhverv, you and your employees will lose access to Digital Post.
Access to Digital Post is associated with the ID number (RID number) connected to your NemID medarbejdersignatur.
If you create a new user in MitID Erhverv instead, the user will be considered a new employee and will therefore not have access to Digital Post.