You don't need a full on PC for 4k. A Raspberry Pi 4 with LibreELEC installed will render 4k just fine whether the file is on the SD card locally or...
It's possible the MFP was on a separate VLAN where only the ports for printing are available to the network segment the computers are on. Many medium...
Call me crazy, but if the customer wants to scan so badly shouldn't it be on them to provide the email to use? That's something they already have for...