PHP mail() does not work & How to prevent spam?

[7rdoq]

Hi TGates

After find from your link, I installed sendmail with cmd

Code:

yum install sendmail sendmail-cf sendmail-doc sendmail-devel

then tried to send, but it no success

I can not find any mail log at /var/log/mail or /var/log

But when I used cmd: sendmailconfig, console alert

Code:

You have new mail in /var/spool/mail/root

Open it, I see warning

----- The following addresses had permanent fatal errors -----
<xxx@gmail.com>
    (reason: 550-5.7.1 [23.227.172.88] The IP address sending this message does not have a)

   ----- Transcript of session follows -----
... while talking to gmail-smtp-in.l.google.com.:
>>> DATA
<<< 550-5.7.1 [23.x.x.x] The IP address sending this message does not have a
<<< 550-5.7.1 PTR record setup. As a policy, Gmail does not accept messages from
<<< 550-5.7.1 IPs with missing PTR records. Please visit
<<< 550-5.7.1  https://support.google.com/mail/answer/8...entication for more
<<< 550 5.7.1 information. f78si2729769otf.316 - gsmtp
554 5.0.0 Service unavailable