Downloading attachments with a size of 2 Megabytes or less.

using System;
using S22.Imap;

namespace Test {
    class Program {
        static void Main(string[] args)
        {
            using (ImapClient Client = new ImapClient("imap.gmail.com", 993, "username",
              "password", AuthMethod.Login, true))
            {
                // This returns all messages sent since August 23rd 2012.
                IEnumerable<uint> uids = Client.Search(
                    SearchCondition.SentSince( new DateTime(2012, 8, 23) )
                );

                // The expression will be evaluated for every MIME part of every mail message
                // in the uids collection.
                IEnumerable<MailMessage> messages = Client.GetMessages(uids,
                    (Bodypart part) => {
                     // We're only interested in attachments.
                     if(part.Disposition.Type == ContentDispositionType.Attachment)
                     {
                        Int64 TwoMegabytes = (1024 * 1024 * 2);
                        if(part.Size > TwoMegabytes)
                        {
                            // Don't download this attachment.
                            return false;
                        }
                     }

                     // Fetch MIME part and include it in the returned MailMessage instance.
                     return true;
                    }
                );
            }
        }
    }
}