PHP must have access to the Sendmail binary during compile time if its mail() function is desired. However, Exim can replace sendmail as shown how in this tutorial.
Generating an email message as a result of some user action from a web page is a common occurrence. It can be done very easily with PHP's mail function. But in order for mail services to be available, a mail server must first be set up.
Under Windows a mail server is defined in the php.ini file using the SMTP option. For the mail functions to be available on a Linux or similar machine, PHP must have access to the Sendmail binary during compile time. If it doesn't exist then the mail function will not be available.
However, Sendmail has a history of being flexible to the point of being difficult to install, configure and maintain. Several other mail servers have been written to act as "Sendmail replacements" and are easier to manage. One such replacement is Exim.
Exim is easier to configure and maintain than Sendmail, and can be installed as a full replacement for Sendmail. Any agent that sends mail by calling Sendmail would actually send the message using Exim instead.
In this tutorial I will show my basic installation and configuration of Exim as a Sendmail substitute to provide PHP with mail capabilities.
