宝塔面板无法使用PHP自带函数发送邮件的解决方法

Centos6.x:

检查sendmail是否启动： 
chkconfig --list | grep sendmail

若显示为空请通过以下命令设置sendmail自动启动：
service sendmail start
chkconfig --level 2345 sendmail on

Centos7.x:
检查sendmail是否启动： 
systemctl list-units --type=service|grep sendmail

若显示为空请通过以下命令设置sendmail自动启动：
systemctl start sendmail.service
systemctl enable sendmail.service