public ArrayList<String> getExternalUsersByMeetingID(int meetingID){
        ArrayList<String> externalUsersReturn = new ArrayList<>();

        for(ExternalUser externalUser : externalUsers){
            if(externalUser.getMeetingID() == meetingID && !externalUsersReturn.contains(externalUser.getEmail())) externalUsersReturn.add(externalUser.getEmail());
        }

        return externalUsersReturn;
    }