I'm having an issue with an Indesign file that I am saving in an epub format. I created this file with Adobe fonts and stock and have a disk scan with no issues. It is not until I save it as an epub format that I have a problem. When I attach the file to various email accounts, they all come back as "undeliverable due to malware detected." Has anybody else had this problem?
Have you scanned the EPUB with one or more virus/malware detectors? It's possible it contains a random string that matches a virus fingerprint.
Have you tried sending the EPUB from another email account, preferably on a different provider? It's not unusual for one mail system (especially one on a shared domain/server) to get flagged for spam or malware and it might be that more than the specific file.
— | Word & InDesign to Kindle & EPUB: a Pro Guide (Amazon)