I have asked around within the support and engineering depts. and could not find any specific info about this scenario. I did learn a little about the sendmail setup though. If your host is using a sendmail setup for the mailing this is fine. Rather than referring to a form parsing and mailing script I think your hosts sendmail configuration is referring to the method used behind the scenes when a script sends an email message.
If you can provide a sample php script with the mail() function being called we should be able to get your UE page working for you.