Programming :: Doing SQL Stuff From Received Email Messages

I was wondering if you could recommend a simple way to achieve functionality where received email messages are automatically processed and used in SQL commands (depending on certain criteria, of course). For example, say I have made a PHP-based blog application and it's located at example.com and I'd like to give members the option of posting to their blogs by sending email to a special @example.com address. The email messages received there will be inserted into a database depending on the sender's address, with the body becoming the post and the subject line becoming the post's title, etc.

Another example could be how those trouble ticket systems let customers submit tickets via email, while the support agents operate via a database-driven Web application. Is this the type of thing one must code from scratch, or is there an open source solution out there which only needs to be configured accordingly?