Follow these steps to stop email loops from specified email addresses. This is different than the KB article 116088 (https://support.software.dell.com/es-es/k1000-systems-management-appliance/kb/116088) in that 1) you do not have to turn off the "Accept email from unknown users", 2) you can specify a list of email addresses you specifically want to block, 3) it doesn't rely on a time interval to take effect. I needed these options as we have certain emails from unknown users come in occasionally, such as software license renewals, ssl renewals, new hires, other helpdesk systems, etc. This will also work for Out of Office replies if needed if you put the user email in the list.

The way this will work is it sets the submitter to unassigned so that Kace doesn't have an email to send it back to. When Kace receives an email, it will automatically send a confirmation back to the user, unless you have that option turned off. If it is received from an unknown or outside user, Kace will create an account for them when you have the "Accept email from unknown users" option checked. If an email address is listed in this custom ticket rule, once it saves the ticket (which it does on creation), it sets it to Unassigned for the submitter. While the system will send one email out when it creates the ticket, and the end system may send a reply, Kace will not send anything back out again, because the ticket does not have a submitter for it. So, you stop the email loop after one replied email, instead of a timed interval.

WARNING: This will execute an update query on the database. Proceed carefully. You are responsible for damages to the database.

1. Go to Helpdesk>Configuration>Rules

2. Click on Choose Action>New (Wizard)

3. Choose "Ticket Submitter User Name", select "=", and then type the email address you want to block (or anything, for that matter. will be changed later), then Next

4. Choose "Ticket Submitter User Name" again, ("change value to" should be selected), then put a 0 in the change to field. Click Done.

5. On the next screen, you will see the SQL select query. Scroll to the bottom to the where clause. Find the
USER.USER_NAME = 'sample@emaildomain.com' entry.
Change it to
USER.EMAIL RLIKE 'email1@email.com|email2@email.com|email3@email.com' 
The Syntax is important here. USER.EMAIL matches the email account of the submitter. RLIKE matches a regular expression, which in this case is a pipe (|) delimited list (or just one email. thats up to your situation) in single quotes. Do not delete any of the parenthesis. This may break your query.

6. You can preview the tickets it will find before applying the rule by clicking the "View Ticket Search Results" link.

7. Check "Email results" and enter your email if you'd like to be notified when the rule is fired off.

8. Verify the "Run update query" box is checked,  and that it has:

update HD_TICKET, USER as T5
    set HD_TICKET.SUBMITTER_ID = 0
  where
        (HD_TICKET.ID in (<TICKET_IDS>))

In the box. This will set the submitter to "Unassigned", virtually eliminating the reply to address.

9. Set the schedule to "On Ticket Save"