In /etc/resolv.conf it's written
the name of the server is nestor.org.gr
and the mentioned ip's are the primary and secondary DNS I have gave for the server when I was installing fedora. I gave the same DNS for the domain www.nestor.org.gr
in ISPConfig. The server's ip is 188.8.131.52
When I am using webmail (UebiMiau) I can recieve and send e-mails. The problem is only when I use outlook to send e-mail.
Thank you for your prompt reply