In WAMP, you can setup an external SMTP server for PHP to send mail, but in LAMP, it's not the same story. You have to configure it manually to make it functional.
In this post, we introduce some steps to resolve PHP mailing problem. I assumed that you already have the PHP code for testing the mailing function.
Comment out SMTP Entry in php.ini
We should comment out SMTP entry in php.ini, so we searched for an entry called SMTP and comment it out by a semicolon as below:
[root@test ~]# vi /etc/php.ini
;SMTP = localhost
Make Sure sendmail has been Installed
We should make sure that sendmail has been installed. If not, please install it.
[root@test ~]# rpm -q sendmail
[root@test ~]# yum install sendmail
Restart the server to make sendmail to take over the mailing function.
[root@test ~]# init 6
Check sendmail Status
Check the status of sendmail.
[root@test ~]# service sendmail status
sendmail (pid 2496) is running...
sm-client (pid 2495) is running...
For EL7 or later, you may use this:
[root@test ~]# systemctl status sendmail
It seems functional, we can try to execute the PHP code again, but in fact, it failed.
Check the /var/log/maillog and see what happened.
[root@test ~]# tail -f /var/log/maillog
Jan 6 20:38:11 test sendmail: NOQUEUE: SYSERR(apache): can not chdir(/var/spool/clientmqueue/): Permission denied
There might be sendmail errors NOQUEUE: SYSERR(apache) due to permission issue, we can solve it by turning it ON in SELinux.
Now, it's working.