I use Timeslips 2015.

I had two clients call saying that the invoices I emailed to them couldn't be opened because their systems indicated a virus had been detected.  The invoices were saved as pdf directly from Timeslips and saved.  I emailed outside of Timeslips through Outlook.  Does anyone have any ideas why this is happening?  My office IT guy scanned the invoice using ESET and said it was virus free.  BTW, ESET is the same antivirus software that the client has!

Any ideas would be greatly appreciated!

~Julie