I really don’t like having sendmail running on a webserver, but some features of WordPress just don’t work if it can’t send email (user registration, for example). Still, WordPress offers support to send email through external SMTP servers instead if a local mailer.
/wp-includes/pluggable.php around line 377, change
/wp-includes/class-phpmailer.php around line 155, set your SMTP host:
var $Host = "my.smtphost.com";
You may also need to set a username and password, and tell WP to attempt authentication. You’ll see those in the lines below the hostname variable.
var $SMTPAuth = true; var $Username = "username"; var $Password = "password";