Ubuntu 16 + Wordpress + WP Mail SMTP + PHP Applications on server can't connect to SendGrid or Other SMTP Relay
I'm new to server management. I've installed LAMP stack and setup Wordpress on main domain and a PHP script on sub domain... After it I want SendGrid SMTP to be used by Wordpress web and by script, I do it on Wordpress by WP Mail SMTP plugin and setup SendGrid API in it and click save when I go to check this out, I go to wordpress login page then forgot password and type my email in it and hit enter but it gives me error PHP mail() function is disabled on my server! After it I open WP Mail SMTP and change the settings from SendGrid to None (System Defaults) and click save, now i again go to check this by going to forgot password entered my email and press enter, Email send successfully! On my email I've received password reset email by root@localhost, Same error with other PHP script on which in script SMTP settings i put all SendGrid SMTP values and click save but it gives me "Connection Failed" error!
Please help me :')