New Post: messaje.Seen = true isn't working properly :S

Hi!
First, congrats for the lib, is really easy to use and get results very fast!,
but I'm experience some problems while marking messages as read.
I'm connecting to a zimbra mail server (version 8) with success, also i can download attachments, but the when i fetch "UNSEEN" messages and using Seen property the first time aren't marked at all, but a second time fetching the same mail it correctly marks as seen, so i'm a bit confused with this.

My code:

 Folder folderInbox = clienteCorreoImap.Folders.Inbox;
                    folderInbox.Messages.Download("UNSEEN", ImapX.Enums.MessageFetchMode.Tiny);
                    foreach (Message msj in folderInbox.Messages) {
foreach (Attachment adjunto in msj.Attachments)
                        {
adjunto.Download();
//saving the file, then i apply some custom processing

//finally i try to mark the message as read
msj.Seen = true;
}
}

i also tried with

msj.Seen = true;
msj.Flags.Add(ImapX.Flags.MessageFlags.Seen);
msj.Flags.Remove("UNSEEN");

With the same results: only the second time fetching and processing the UNSEEN mails they got correctly marked as seen.
I could use NEW or RECENT to fetch mails, but i need to keep track of mails which aren't correctly downloaded and processed its attachments (ie, keep them as unread/unseen), so that's why I'm using the UNSEEN tag.
If you could help me to enlight what I'm doing wrong here would be greatly appreciated

Thanks! And keep the good work!