For the Mail functions to be available, PHP must have access to the
sendmail binary on your system during compile time.
If you use another mail program, such as qmail or postfix, be sure to
use the appropriate sendmail wrappers that come with them. PHP will
first look for sendmail in your PATH, and then in
It's highly recommended to have sendmail available from your
PATH. Also, the user that compiled PHP must have
permission to access the sendmail binary.
Where the sendmail program can be found,
usually /usr/sbin/sendmail or
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
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.