MailCore.m

#import <MailCore/MailCore.h>
#import <MailCore/MCOIMAP.h>

- (void)loginToServer:(NSString*)server withUsername:(NSString*)username andPassword:(NSString*)password {
  MCOIMAPSession *session = [[MCOIMAPSession alloc] init];
  session.hostname = server;
  session.port = 993;
  session.username = username;
  session.password = password;
  session.connectionType = MCOConnectionTypeTLS;
  
  // Use credentials to fetch messages in INBOX
  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) {
      // Yay! I just logged into a mail server...
  }];
}