I can not duplicate your issue as reported. The message is properly marked as read. My guess is that you have some side effect produced by one of:
- Multiple normal rules acting on those messages.
- Custom sieve script.
Here is how I made my test:
- On a test account with only one other existing rule, I create a rule as follows.
- From *@gmail.com
- Only these three boxes are checked:
- Mark as read
- Send to spam
- Apply to... New matching messages on arrival
I then sent test messages from my Gmail account to that Fastmail account. They all arrived in the spam folder marked as read (not bold).
When I uncheck "Mark as read", the messages arrive as expected as unread (bold).
Bill