Behaviour of mail without subject

I’m new with eM Client and try this with one e-mail address. My first impression was it is really nice and check it deeper if I can change from Thunderbird.
The first what I saw, what is not really nice is, I have some mails in subfolders which have no subject. All these mail are listed in the first / highest subfolder with the newest mail without subject. The settings are mail sorted by conservation.
My expectation is, this setting is only for the subfolder not for the complete e-mail-account. For my point of view this is an error.

I think the messages without a subject are being grouped together as a conversation.

Conversations include messages from all folders, not just the one you are in. Unfortunately that cannot be changed, so you might want to disable conversations if this is a problem for you. To do that select Menu > View > Conversations > Disable Conversations.

Sorry Gary, but both Thunderbird and Outlook can handle this only in the current directory. This is a K.O.-criteria for me.

Yeah, threads and conversations are not really the same thing. A thread usually only has the related messages from the current folder, whereas a conversation includes all messages regardless of what folders they are in. Thunderbird does a threaded view for the current folder, but no conversations. eM Client does conversations, but no threaded view. Can’t say what MS Outlook does though.