I found some steps for allowing mixed size originals for scanning for your device that may help you:
We've have multiple Xerox 7535's (all with the latest firmware) and we are having issued scanning to email.
The scan settings are we have used are the recommended ones from Xerox and the scan size is set to allow 20Mb scans.
The issue we have is that we we try to scan a document with A4 & A3 then it doesn't scan properly.
We have tried scsanning multiple documents, all of the same paper size and they work perfectly. e.g. an 84 page full colour document, A4, scans at a size of 10Mb and works.
But if I try a 30 page A4 document with 1 A3 page (inserted around Page 10), it scans the first 26 pages perfectly and the last 4 pages scan all black. The file size reported is only 4Mb.
I did 7 scans in a row with 3 printers alternating between all A4 and A4 & 1 page of A3. Each of the A4 only scans came out perfectly and each of the A4 & A3 scans failed at page 27 with the last 4 pages showing up as a big, full page, black box.
Can anyone help with this please?