ZD IMAP doesn't save a message in sent folder if delivery failure

[cecco]

Hi,
I have a zimbra server and using ZD with it all works ok.
In ZD i have also an external IMAP account on a ISP. everything is ok except for this little problem:
If i sent a mail to a wrong address i get back the delivery failure message from the smtp server of my isp (this is ok), but if i go to the sent folder looking for the sent mail (for edit as new and correct the recipient) the mail isn't there.
As I have said above in the zimbra account this is working

There are some settings i can change? i have looked around without luck

Thank you
Francesco