eMC doesn’t track flags properly. If not set within eMC itself (e.g. on the server with Sieve), flags like Seen (read) or Flagged (important) are not shown / counted automatically unless the message is delivered to an account’s inbox. If delivered to a subfolder eMC ‘sees’ the flag only when one opens that folder - F7 does not help.
That renders common folders like ‘Unread’ or ‘Important’ more or less useless.
I’d say: not fit for production purposes.
what version of eM Client does this happen with?
Is the Sieve account set up as IMAP or Exchange?
Does it happen with any other accounts?
eMC’s version is 7.0.27943.0.
I’ve done some tests and came to the conclusion that it’s eMC’s buggy handling of flags which is the problem. Sieve’s got nothing to do with it. Any software which sets flags (\Seen or \Flagged) on the server (e.g. another mail client) can confuse eMC.
I’ve recorded a screencast showing the problem: https://www.jgid.de/_static/vid/emc-syncing.mp4