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I can send email within my domain but can't send to external addresses like @yahoo.com or @gmail.com. my mail server is "abc.def.ghi".

I tried telneting in commandline to someone@yahoo.com. and it says unable to relay.

telnet abc.def.ghi smtp
Trying xx.xxx.xxx.xx...
Connected to abc.def.ghi.
Escape character is '^]'.
220 abc.def.ghi Microsoft ESMTP MAIL Service ready at Thu, 23 May 2013 16:05:51 +0800
250 abc.def.ghi Hello [xx.xxx.xxx.xx]
mail from:<mailer@somewhere.com>
250 2.1.0 Sender OK
rcpt to:<someone@yahoo.com>
550 5.7.1 Unable to relay

These are the contents of my /etc/postfix/main.cf. i think it's the default configuration. I only added the relay host option.

queue_directory = /var/spool/postfix
command_directory = /usr/sbin
daemon_directory = /usr/libexec/postfix
mail_owner = postfix
inet_interfaces = all
inet_protocols = all
unknown_local_recipient_reject_code = 550
alias_maps = hash:/etc/aliases
home_mailbox = Maildir/
debug_peer_level = 2
debugger_command =
     ddd $daemon_directory/$process_name $process_id & sleep 5
sendmail_path = /usr/sbin/sendmail.postfix
newaliases_path = /usr/bin/newaliases.postfix
mailq_path = /usr/bin/mailq.postfix
setgid_group = postdrop
html_directory = no
manpage_directory = /usr/share/man
sample_directory = /usr/share/doc/postfix-2.6.6/samples
readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES
mynetworks =
relayhost = abc.def.ghi

Thanks in advance for helping out.

share|improve this question
Are you sure you connected to postfix? 220 abc.def.ghi Microsoft ESMTP MAIL Service ready looks like Windows to me... –  etagenklo May 23 '13 at 8:38
Why would you put youself in relay hosts? –  NickW May 23 '13 at 8:52
hi etagenklo what do u suggest i do? im very new to this and i'm not getting the support of our it persons. they're not well versed in linux. –  lloyd May 23 '13 at 9:05
hello NickW. im not sure. i just tried out some how to's that i find in google. any suggestions? –  lloyd May 23 '13 at 9:06
Well, a relay host is normal another server that you send mail through. So mail would arrive at your server, and you would relay it through your ISP's server, or another.. –  NickW May 23 '13 at 9:20

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