Calendar - On cancel appointment can't send with the set account

[ratasoft]

If I configure an account "to respond" in preferences when I create an appointment with other account at this moment work fine even when the appoinment change, but if I cancel the appointment the notification mail is send by the main account.

Example:

- I have a zimbra account main@domain.local...

- In preferences I configure an POP account external@domain.com...

- I create an appointment in my calendar, the organizer external@domain.com and the mail is sent to the attenders...

- The participant receive the appointment and accept, but I need modify the appointment...

- The mail with modification is sent with the changes, at this moment is ok, even the attenders see that the organizer's mail is external@domain.com and the calendars do update ok...

- But if the organizer cancel de appointment the mail is sent by the main@domain.local...

This is a problem if I use a external MTA to deliver the mails, because is rejected.... (the attender can´t receive the mail).

Is a bug?