## Runtime Configuration

The behaviour of these functions is affected by settings in php.ini.

Mail configuration options
Name | Default | Changeable | Changelog
--- | --- | --- | ---
mail.add_x_header | "0" | PHP_INI_PERDIR | Available since PHP 5.3.0.
mail.log | NULL | PHP_INI_PERDIR | Available since PHP 5.3.0. (PHP_INI_SYSTEM|PHP_INI_PERDIR)
mail.force_extra_parameters | NULL | PHP_INI_PERDIR | Available since PHP 5.0.0. (PHP_INI_SYSTEM|PHP_INI_PERDIR)
SMTP | "localhost" | PHP_INI_ALL |
smtp_port | "25" | PHP_INI_ALL |
sendmail_from | NULL | PHP_INI_ALL |
sendmail_path | "/usr/sbin/sendmail -t -i" | PHP_INI_SYSTEM |

For further details and definitions of the PHP_INI_* modes, see the Where a configuration setting may be set.

Here's a short explanation of the configuration directives.

`mail.add_x_header` bool

  Add `X-PHP-Originating-Script` that will include UID of the script followed by the filename.

`mail.log` string

  The path to a log file that will log all mail() calls. Log entries include the full path of the script, line number, `To` address and headers.

`mail.force_extra_parameters` string

  Force the addition of the specified parameters to be passed as extra parameters to the sendmail binary. These parameters will always replace the value of the 5th parameter to mail(), even in safe mode.

`SMTP` string

  Used under Windows only: host name or IP address of the SMTP server PHP should use for mail sent with the mail() function.

`smtp_port` int

  Used under Windows only: Number of the port to connect to the server specified with the `SMTP` setting when sending mail with mail(); defaults to 25.

`sendmail_from` string

  Which `"From:"` mail address should be used in mail sent directly via SMTP (Windows only). This directive also sets the `"Return-Path:"` header.

`sendmail_path` string

  Where the sendmail program can be found, usually /usr/sbin/sendmail or /usr/lib/sendmail. configure does an honest attempt of locating this one for you and set a default, but if it fails, you can set it here.

  Systems not using sendmail should set this directive to the sendmail wrapper/replacement their mail system offers, if any. For example, » Qmail users can normally set it to /var/qmail/bin/sendmail or /var/qmail/bin/qmail-inject.

  qmail-inject does not require any option to process mail correctly.

  This directive works also under Windows. If set, smtp, smtp_port and sendmail_from are ignored and the specified command is executed.