Email being marked as read on iPhone and iPad without being read on either device or eM client on PC

I’m using eM client as a my desktop email client for an email address (custom domain). The client syncs everything fine on the desktop but my emails are now appearing on my iPhone and iPad as read, even when I’m out of the office and my pic is turned off. If I manually fetch the emails on my devices they sometimes come through as unread but if they are pushed or fetched automatically they are appearing as read. This is getting very frustrating as I’m missing lots of emails when I’m away from my desk because they aren’t being flagged on my phone. This problem only started occurring since using eM client. I have unticked the two read mail settings, ‘mark read after X seconds’ and ‘Mark read after opening in a new window’. I’ve seen lots of similar problems but can’t find the definitive answer to solve the problem. If it doesn’t get solved I’m going to have to get rid of em client all together. Any help would be appreciated.

Hello Tom,
does this happen only on one account or on all accounts in this device?
If it’s just one account, please tell me which one it is and if it is set up as IMAP or POP on other devices.