I am desperately searching for help on accomplishing the following...

How do I enable a third party user to add records via POST method to my mysql database and, have a "welcome" email sent to all the new records?

To help you understand better what I'm looking for, this would be used so that a lead-generation company (providing leads for my business) could do the real-time posting of leads to my database, then the email would automatically be triggered through php.

I have talked with a couple of companies that provide these leads and they have told me that I need to provide them with a POST url and a datastring.

Any ideas?

the only fields I need in the record are firstname, lastname, email address.

Could you provide us with more detail?

For example what programming language are you attempting to accomplish your goal? If you don't know then what type of server is your site Hosted on? Your options are really only limited by what your server supports, therefore if you're on a Windows server, you won't be able to run your site in PHP.

Also this post might get better responses in the Programming section.