ImapClient.Search does not return new messages

[benfoster]

I'm keeping our ImapClient alive and polling periodically for new messages with the following code:

    public IEnumerable<Message> GetMessages()
    {
        foreach (var msgId in client.Search(SearchCondition.Unseen()))
        {
            var msg = client.GetMessage(msgId, headersonly: false, setseen: true);

            foreach (var attachment in msg.Attachments)
            {
                yield return new Message
                {
                    ContentType = attachment.ContentType,
                    Filename = attachment.Filename,
                    Data = attachment.GetData()
                };
            }
        }
    }

I'm finding that any new emails are not returned. Do I need disconnect/reconnect between polling in order to pick new mail/clear the queue?