I have a POP3 email account and I normally read my email on my (Windows) PC. As I had a long vacation coming up and wanted to stay in touch, I installed K9 email on my Samsung Galaxy S3 and set it up to retrieve emails from my POP3 account. I tested it and all appeared to be working fine. While I was away, I checked my email frequently. Most days I picked up maybe up to a dozen emails so I assumed everything was still working OK. The problem became apparent when I got home and fired up my PC. After three weeks away, Microsoft Outlook reported over 400 emails sitting in my in-box, some dating back to the very start of my vacation. The vast majority of these I'd never seen before. In other words, they never showed up when I checked my email using K9. Why not? Can anyone think of a reason why some, but not all, POP3 emails are visible on my Android phone using K9?