Is it possible to send an invoice as text in an email only? ...withoput any attachment.

Hi.
I have a customer who is complaining that our invoices are being blocked by security filters that are reading it as potentially harmful email. They say that they cannot retreive it and asking to have it sent as a text file or text in an email.

Is there a way to set up an email template that draws the inforamtion from the invoices module?
Other than that I can't see any way to do this unless I manually create a text invoice.
This only happens occasionally but it would be good to have this option.

I tired to use the contacts email but it won't use any invoice category templates.
If I create the template and try to send it from the invoice view then I have to create an attachment to send the email as there is no option to send without attaching a file. Simplest solution would be to create that option in the drop list.

Any other possibilities?

cheers,
Danny.