It seems that replies sent by hotmail aren't accepted by the Hostgator's system, the error is as follow:
A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:
pipe to |/usr/bin/php -q /home/centur/public_html/support/api/pipe.php
generated by info AT century DOT
local delivery failed ( I changed the code because the site isn't live yet.)
But what's weird is that new e-mails and the replies by me work fine, but when I try to reply to that ticket in hotmail, this error appears.
This problem is weird because if the pipe config was wrong, I shouldn't be able to send new e-mails and reply to them with osTicket.
I don't have this problems with other e-mails such as gmail, my ISP e-mail....
Oh, and our host is hostgator.com
I think I should explain with a new diagram:
New hotmail e-mail --> osTicket: Yes
OsTicket reply --> Hotmail: Yes
Last reply in hotmail --> osticket: No go.