InfoPath Dev

Hi, we Have a requirement that we need to get user details based on email id given by user. i'm using GetUserProfileByName data connection using udcx files, to query this data connection we need to set Accountname so m setting domain/email (eg of email id: [email protected]) for Accountname. its working fine for most of the users but for few users it shows an error. so i need to set domain/username to Accountname in GetUserProfileByName data connection. I need to get userName using email.

 I don't think there is a way to get the user name via email - what is the error for the users where it shows an error? Wouldn't it be better to address the root cause?