I did create a scan to email app within the app studio and the email scan works fine and reaches the recipient.
My problem though is that compared to the normal scan to email function, some scan settings configured for scan to email on the machine are not used for the scan with the app.
Two really critical settings would be
a) the image compression settings
and b) the background suppression setting.
From the scan results, both are off when doing an email app scan regardless of the setting on the MFD (tested on a WC6655i and WC7855i).
I was under the impression that even though one cannot use these settings within the app creation, the machine settings would still be applied.
But on the scans from the app one can crlearly see the image on the backside of the paper shining through and one page scanned at 200dpi results in a roughly 500KB pdf - which is huge compared to the compressed scans with the native MFPs scan to email attachments.
So my question would be - Is this an app problem or a machine firmware issue?
And if it's an app issue - would there be any way that this gets changed?
Firmwares on the test machines were 073.040.066.08210 (WC7855i) and 073.110.187.20500 (WC6655i)
Unfortunately, what you have experienced is a known issue. The App and the Device are both at fault, meaning that they both contribute a little to what you have described. There are defects in the system that cover the App issue, as well as the Device problem.
There is some good news, though. The App team is currently developing a solution update and part of what they are adding is the ability to control image quality for scanned output (Scan to Email, specifically). Once this release is available, the user will be able to modify the compression setting within the App. This should resolve the issue with the large file size of the scan that you have noted in this post.
I will check if the background suppression setting has any changes in this upcoming release. If it isn't planned for this release, I will ask if it could be considered for a near future update.