Sendmail & FormMail issue

After searching through the forums, I haven't yet found an answer. I have a client with a website that uses a FormMail (http://www.scriptarchive.com/readme/formmail.html) mail script and form. I currently host the clients website only; their email is hosted by a different company on a different box. The client is currently unable to receive mail from the FormMail script.

For the purposes of understanding this message, here are a few global variables for you:

my client's domain name: company.com
client that needs to receive messages from FormMail: recipient@company.com
my client's cPanel login: cpanelusername

After digging into the problem, I have found that FormMail uses sendmail to send out its messages from the form. Unfortunately it appears that sendmail is only able to send mail to local users, and the client's mail users are located on a different machine. In other words, the company's site is located on my machine at www.company.com. The companies mail user, recipient@company.com is unable to receive messages from FormMail because the user is located on a different box.

Since there are no email users set up on my server, all of the messages sent by the script are being delivered to the default domain address, cpanelusername@company.com. So, I thought I would simply change the default email address to recipient@company.com. This is not allowed as the user "recipient" does not exist on my machine.

Any and all help would be appreciated as I am stumped!