My postfix mail server can accept mail from internet & can send mail in my domain only. When I tried to send mail outside the following message is comming

(The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was 'sib@netcomsolutions.in'. Subject 'test', Account: 'mail.nitnagaland.ac.in', Server: 'mail.nitnagaland.ac.in', Protocol: SMTP, Server Response: '554 5.7.1 <sib@netcomsolutions.in>: Relay access denied', Port: 25, Secure(SSL): No, Server Error: 554, Error Number: 0x800CCC79)

Can anybody suggest me the exact problem.

Many ISPs block port 25 to make it difficult for spam to be relayed via home computers.
I think that's what's happening here.

I did a search for "Server Error: 554, Error Number: 0x800CCC79" and got this.

1 members found this post helpful.

There is an old mailserver in Hmail with the present ip address ,same hostname & domain name. When we put the old mailserver online, the mail sending & receiving are working perfectly.Users can receive mail & send mail also. If the ISP block smtp, the old mail server would not send the mail outside.

my postfix mailserver's postconf -n is as follows

[root@mail ~]# postconf -n
alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
data_directory = /var/lib/postfix
debug_peer_level = 2
home_mailbox = Maildir/
html_directory = no
inet_interfaces = all
inet_protocols = all
mail_owner = postfix
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain, mail.$mydomain
mydomain = nitnagaland.ac.in
myhostname = mail.nitnagaland.ac.in
mynetworks = 10.14.20.0/16, 127.0.0.0/8
myorigin = $mydomain
newaliases_path = /usr/bin/newaliases.postfix
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES
relay_domains = $mydomain, $mydestination
relayhost =
sample_directory = /usr/share/doc/postfix-2.6.6/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
unknown_local_recipient_reject_code = 550
[root@mail ~]#