I ́m testing S/MINE at the moment. I found two problems:
If I sent a encrypt message, this message is unread in the sent folder. Also with a rule. If i start the rule manuelly later, the message ist mark as read.
When the message is not encrypt by sent it is mark as read.
It is not possible to search a body text at a signed mail. And not at a encrypt mail. It ́s only possible at a not signed or encrypd mail.
that situation when you read something and you mark it as read (or it is done manually) and it stays in unread until you switch to another folder is normal and it is by design.
so the thing you find as a problems is that sent email is in Unread folder?
well, this is because many users requested this. They sometimes needed to read more emails but wanted to return to those read ones easily without need to search for them in inbox folder, so they stay in unread until you switch to another folder what causes not showing them anymore.