Using older versions of Outlook for Mac in business environments
This is still happening on 15.32 (170309).
If you put an image into a signature directly, it resamples it causing it to blur and look terrible.
If you put a larger image into the signature and resize it down, it still resamples it.
If you compose an email, enter an image, resize it, set it's text-wrap to any of the options, select it and copy it, then paste it into the signature, it no longer looks terrible, but you get the above message twice on inclusion of your email signature.
If the above is not a clear enough report for engineers to reproduce the issue then quite frankly you need to hire better engineers. I am sure that you folks are more than capable of fixing this though.
Alternatively, you could:
i) not resample images placed into email signatures
ii) provide some guidance as to image formats and resolutions required by Outlook.
I hope for a speedy response and fix.
Regards,
Adam