Error when trying to mail PO to a vendor

Hi,

we're on ECC 5.0. SAPKB64015.

I'm testing the email of a PO to a vendor. I've set up the condition record, and the vendor has an email address. I'm using output type NEU. This is set up with the standard smartform /SMB40/MMPO_L program /SMB40/FM06P form routine ENTRY_NEU. When I create a PO - I go into messages and get the error 'Archiving format not equal to PDF.' - message number SSFCOMPOSER 017.

Any ideas why this isn't working?

Thanks

Richard