You can set a rule for mass reply to all emails at once in a specific folder.

Part 1: Create a new email message and save it as Outlook Template

1. Firstly, you need to create a new folder and move all the emails which you want to mass reply with same content into.

2. Create a new email with the content you want to reply. (Note: You need to type in the email subject but keep the To field blank). See screenshot:

3. After composing the new email, please click File > Save As.

4. In the Save As dialog box, please type in your file name in the File name field. By default, the file name will be named with the email subject. And then select Outlook Template from the Save as type drop down menu. Finally click Save button.

Note: If you choose the Outlook Template from the Save as type drop down menu, the file will be saved in the Template folder automatically. Please don’t change the destination folder.

5. When it returns to the Message window, please click the Close button to close it.

6. When an Outlook prompt box popping up, click No button. See screenshot:

Part 2: Create new rule for the template

Now you need to create a new rule for this template.

7. Get into the Rules and Alerts dialog box.
A. In Outlook 2007, click Tools > Rules and Alerts.
B. In Outlook 2010 and 2013, please click Rules > Manage Rules & Alerts under Home tab. See screenshot:

8. In the Rules and Alerts dialog box, please click New Rule button under E-mail Rules tab.

9. When the Rules Wizard dialog box popping up, go to the Start from a blank rule section and select Apply rule on message I receive. And then click Next button.

10. In the next Rules Wizard dialog box, click Next to skip to the next step. When a prompt box pops up, please click Yes button.

11. In next dialog box, check the reply using a specific template box in Step 1. And then click on the text of a specific template in Step 2. See screenshot:

12. In the Select a Reply Template dialog box, you need to: (1) Select User Templates in File System in the Look In drop down list; (2) Select the template you have saved before; (3) Click Open button. See screenshot:

13. When it returns to the previous dialog box, please click Next button.

14. Keep clicking Next button until the last Rules Wizard dialog box showing. In this dialog, type a name for this new rule in the Step 1, uncheck the Turn on this rule box in Step 2, and then click Finish button. See screenshot:

Note: You can rename the rule by removing the old name and typing a new one in the Specify a name for this rule textbox.

15. Click OK button in the following prompt dialog box.

16. When it returns to the Rules and Alerts dialog box, please click OK button to finish the whole settings.

Part 3: Run the rule for the specific folder

17. Restart the Outlook application.

18. Go into the Rules and Alerts dialog box again. Select the rule you have created before, and then click Run Rules Now button under E-mail Rules tab. See screenshot:

19. In the Run Rules Now dialog box, you need to (See right screenshot):
(1) Check the rule box which you want to run later under select rules to run;
(2) Click Browse button to select the folder which you want to mass reply to all the emails inside.
(3) Select All Messages from the Apply rules to drop down list.
(4) Click Run Now button.

Note: If you have subfolders in the selected folder, please check the Include subfolders box.

20. Close the dialog boxes.

Now all emails inside the specific folder are replied with the same content at once.

You can see there are multiple steps you should do in the above method. But with Kutools for Outlook’s Bulk Reply utility, you can easily mass reply to multiple emails at once.

1. Go to the email folder with the emails you want to mass reply to and select them, and click Kutools > Bulk Reply > Create & manage reply template. See screenshot:

2. In the popping up Create & manage reply template dialog box, please (1) click the Add button to add a new reply template, (2) keep the new template selected, and type the template content in the below editing box, and then (3) click the Reply button. See screenshot:

Now all selected emails are replied with the new reply template.

Notes:
(1) If you want to reply to all received emails in a specific folder, please open the folder and then press Ctrl + A keys on the keyboard to select all emails at once.
(2) If you have added reply templates, after selecting emails, you can reply all of them by directly clicking the existing template in the Reply multiple messages drop down list.