Oct 24 12:50:49 mail2 postfix/smtpd[9280]: connect from unknown[192.168.5.240] Oct 24 12:50:49 mail2 postfix/smtpd[9280]: NOQUEUE: reject: RCPT from unknown[192.168.5.240]: 504 5.5.2 <dzDevelop>: Helo command rejected: need fully-qualified hostname; from=<lon@mail2.yinghuan.com> to=<lon@mail2.yinghuan.com> proto=ESMTP helo=<dzDevelop> Oct 24 12:50:49 mail2 postfix/smtpd[9280]: NOQUEUE: reject: RCPT from unknown[192.168.5.240]: 504 5.5.2 <dzDevelop>: Helo command rejected: need fully-qualified hostname; from=<lon@mail2.yinghuan.com> to=<gng@yinghun.com> proto=ESMTP helo=<dzDevelop> Oct 24 12:50:49 mail2 postfix/smtpd[9280]: disconnect from unknown[192.168.5.240] Oct 24 12:52:11 mail2 postfix/smtpd[9280]: connect from unknown[192.168.5.240] Oct 24 12:52:11 mail2 postfix/smtpd[9280]: NOQUEUE: reject: RCPT from unknown[192.168.5.240]: 504 5.5.2 <dzDevelop>: Helo command rejected: need fully-qualified hostname; from=<lon@mail2.yinghuan.com> to=<lon@mail2.yinghuan.com> proto=ESMTP helo=<dzDevelop> Oct 24 12:52:11 mail2 postfix/smtpd[9280]: NOQUEUE: reject: RCPT from unknown[192.168.5.240]: 504 5.5.2 <dzDevelop>: Helo command rejected: need fully-qualified hostname; from=<lon@mail2.yinghuan.com> to=<gng@yinghun.com> proto=ESMTP helo=<dzDevelop>
经过努力探索，发现只需要修改postfix的配置文件即可，我的版本postfix配置文件位于/etc/postfix/main.cf
用编辑器打开vim /etc/postfix/main.cf，找到smtpd_helo_restrictions这一行，按照下面修改后保存。
smtp_data_xfer_timeout = 600s smtpd_helo_required = yes #smtpd_helo_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_non_fqdn_helo_hostname, reject_invalid_helo_hostname, check_helo_access pcre:/etc/postfix/helo_access.pcre #上面一行修改下面的内容，去掉reject_non_fqdn_helo_hostname smtpd_helo_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_invalid_helo_hostname, check_helo_access pcre:/etc/postfix/helo_access.pcre
重新启动postfix
service postfix restart
再次发送，ok了
解决iredmail下postfix发送邮件时报错[need fully-qualified hostname]
原文：http://www.cnblogs.com/dajianshi/p/4048066.html