Excel file opening problem

Dear Sir / Madam
We are using lotus notes messaging system, from this i had sent a XL file to our MD, the file is in a good condition and can able to open. Our MD is having a yahoo account and using outlook express mail client. when he tried to open an excel file i had sent, he is getting a following error.

Filename cannot be accessed. The file may be read-only, or you may be trying to access a read-only location. Or, the server the document is stored on may not be responding

i dont know how to resolve this, kindly help

Manikandan V
India