gistfile1.m

MCOIMAPSession *session = [[MCOIMAPSession alloc] init];
session.hostname = @"imap.gmail.com";
session.port = 993;
session.username = @"matt@gmail.com";
session.password = @"password";
session.connectionType = MCOConnectionTypeTLS;

MCOIndexSet *uidSet = [MCOIndexSet indexSetWithRange:MCORangeMake(1,UINT64_MAX)];
MCOIMAPFetchMessagesOperation *fetchOp = 
  [session fetchMessagesByUIDOperationWithFolder:@"INBOX"
                                     requestKind:MCOIMAPMessagesRequestKindHeaders
                                            uids:uidSet];

[fetchOp start:^(NSError *err, NSArray *msgs, MCOIndexSet *vanished) {
    NSLog(@"Fetched all the message headers!.");
}];