To show new appointments as free/busy/tentative by default in Outlook, you need to create an appointment form which shows time as free/busy/tentative, and then replace the default appointment form in your Outlook.

1. Open the specified calendar, and click Home > New Appointment to create a new appointment.

2. In the new appointment window, please specify Free (Working Elsewhere, Tentative, Busy, or Out of Office as you need) from the Show As drop-down list on the Appointment tab. See screenshot:

3. Go ahead to click Developer > Design This Form. See screenshot:
Note: Click to view how to add the Developer tab on the Ribbon in Outlook.

4. Click Developer > Publish > Publish Form. See screenshot:

5. In the Publish Form As dialog box, please (1) make sure Outlook Folders is chosen in the Look In drop-down list, (2) Type the Show time as an option you specified (Free in my example) in the Display name box, and then (3) click the Publish button. See screenshot:

6. Close the new appointment without saving.

7. Now you return to the Calendar, please right click the specified opening calendar and select Properties from the right-clicking menu. See screenshot:

8. In the Calendar Properties dialog box, please select the new form (Free in my example) from the When posting to this folder, use: drop-down list, and click the OK button to save the change. See screenshot:

Now you will see the New Appointment button is replaced with the New Free button (or another name depending on the form name you specified in Step 5) as below screenshot shown. And clicking the New Free button will create a new appointment showing time as free automatically.

Automatically reply with the default email account in Outlook

In general, Outlook can identify the email account that the active email belongs to, and then reply with this email account automatically. However, with Kutools for Outlook's Always reply with default account option, no matter which email account the active email belongs to, it will be replied with the default email account in you Outlook.