osTicket 1.11(stable) : every time we respond to a ticket it automatically creates a new ticket, please we need your help.
I used php7, database mysql.

How are you "respond"-ing to a ticket?

there is a text field at the bottom of the message with a reply

7 days later

@sipe

This means you are replying to a System Email.....stop replying to a system email.

Cheers.

24 days later

The ticket is created when the user sends a mail to the system mail. And when I try to answer a new ticket is created

So user sends an email from user@domain.tld to supportemail@domain.tld.

You log into the instance using an agent account.
You look at the ticket.
You type in a response.
You click submit.
And the ticket does not get updated... and it creates a new ticket?
That makes zero sense to me.

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