[size=3]What is this?[/size]
You're looking at the wiki page dedicated to the Postmark library for CodeIgniter.
Postmark is a transactional e-mail delivery service from Wildbit. Transactional e-mails are the e-mails generated by a web application after an user action such as registration, requesting a password reminder, receiving a reply to a comment, etc. The problem me and many developers faced is that sometimes the client's servers are blacklisted and these e-mails land in the users' spam folder. This is where Postmark comes to the rescue, hopefully – instead of using the built in mail function of your web development language of choice you issue a call to Postmark which sends out the e-mail from their “well regarded” servers so that hopefully they land in the user’s inbox.
For more information and download visit the library's page.