PDF Invoice encryption

[Aprisa]

I need some help re-the above:-
We are trying to get customers to receive their invoices via a pdf attachment email.

All is fine except for one customer who's system is rejecting the mail because it says it has 256bit encryption?

Nothing is set in Outlook to encrypt attachments and so I am at a loss as to how to proceed, is there any way to prevent this encryption?
Thanks
Nick

[buggalugs]

Its likley to be some over-zealous anti-spam or anti-virus scanning that's bouncing it because it can't process it for some reason, the encryption bit might be a red herring. Could be old software that won't read the new PDFs or something. You could randomly fiddle with the options in your PDF creator, or try a different one to see if that can work around the problem. Or get the far end to tweak their settings ()

[eps]

Are you sure they're not rejecting it because it hasn't got 256 bit encryption?

Can you get them to email you the message they get or a screenshot?