MailKit IMailFolder.Close引发异常

Question

I'm having a method using MailKit that will open a folder in your mailbox. If the acceslevel is lower than the provided argument, then it will close the folder, and then open the folder in the right accesslevel.

Something like this:

public void OpenFolder(IMailFolder folder, FolderAccess level)
{
    if(folder.IsOpen() && folder.FolderAccess < level)
    {
        //Closed folder
        using(var task = folder.CloseAsync())
        {
            task.Wait();
        }
        //Open folder with correct accesslevel
        folder.Open(level);
    }
}

The task.Wait() part is throwing a AggregateException (which seems to have an inner exception by type of ImapCommandException), telling me that:

MailKit.Net.Imap.ImapCommandException: The IMAP server replied to the 'UNSELECT' command with a 'BAD' response.

What I can conclude is that the response from tying to do a CLOSE operation (which according to IMAP4 is UNSELECT), give BAD response, which should be caused by no mailbox selected.

How can I handle this close operation, so that I can close a folder with lower access level, and open it afer closing in the correct accesslevel???

Answer 1

First, I should point out that there is no need to Close the folder before you open another folder or even the same folder with a different access level. The previously opened folder will always be automatically closed for you by the server.

I should probably update the docs to mention this as it seems a lot of people seem to think that they need to close folders.

Anyway, that said, I'm not sure how this could happen. What version of MailKit are you using? There was a bug in some older MailKit versions that did not keep proper folder opened state which may be what you are hitting.