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Installing/Configuring
PHP Manual

## Runtime Configuration

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

Mail configuration options
Name | Default | Changeable | Changelog
--- | --- | --- | ---
SMTP | "localhost" | PHP_INI_ALL |
smtp_port | "25" | PHP_INI_ALL | Available since PHP 4.3.0.
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_* constants, see the php.ini directives.

Here's a short explanation of the configuration directives.

`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. Only available since PHP 4.3.0.

`sendmail_from` string

  Which "From:" mail address should be used in mail sent from PHP under Windows. 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.

Installation
Resource Types
Installing/Configuring
PHP Manual