The SMTP servers consider an email message as delivered the very moment the message has been added to the recipient’s mailbox. In the simplest implementations, the mailbox is nothing but a text file, named after the recipient’s email id (for example ’sales’ for ’sales@sakshay.in’). When a message arrives, the Mail Transfer Agent simply appends it to the bottom of the file.
Now imagine that instead of (or in addition to) collecting the incoming mail in the mailbox file you want to perform automated processing right on your web server. For example, sending an auto response, submitting support ticket, subscribing the sender to a mailing list, spam filtering etc. Obviously you will need to install some program and ensure the program is being invoked every time new email arrives to a designated email address. The program needs to be given an access to the message as well.
The standard technique is to instruct the MTA to
* execute the program every time an email arrives for a predefined recipient (e.g. sales@sakshay.in), and
* send the message content to the program’s standard input
The email piping is the name for the technique of sending email message as an input to a program rather than appending the message to the mailbox file.
How to enable email piping?
Every MTA software package has its own rules and procedures. These rules may be amended by hosting provider. A hosting provider may also install 3rd party server management software (e.g. CPanel), which allows configuring of mail forwarding tables.
This is why there is no way to provide common instructions for configuring MTA software, which was installed and is being maintained by your hosting provider. You should refer to your hosting manual or contact your hosting provider for email piping instructions.
Unfortunately the email piping feature is not available with each hosting account. Windows based servers lack the feature more often than UNIX boxes. Providers of UNIX shared hosting accounts are somewhat reluctant to allow email piping, because normally the user supplied email processing program will be executed with extended permissions and this involves obvious security threats. If your hosting provider does not support email piping, you may use an alternate technique – pop3 account polling.
