(Objective-C) Reading Unread POP3 Email

The POP3 protocol does not provide the ability to ask the server which emails are "unread". Furthermore, a pure POP3 server does not even keep this information. Some servers, such as Exchange Server, expose both POP3 and IMAP interfaces. In these cases, information about read/unread status exists on the server, but it is only available via the IMAP protocol. Email clients such as Outlook and Thunderbird keep read/unread information on the client computer. This example demonstrates how UIDLs can be saved to track and read "unread" email.

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#import <CkoMailMan.h>
#import <CkoStringArray.h>
#import <CkoEmailBundle.h>
#import <CkoEmail.h>

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// The mailman object is used for receiving (POP3) 
// and sending (SMTP) email.
CkoMailMan *mailman = [[CkoMailMan alloc] init];

// Set the POP3 server's hostname
mailman.MailHost = @"pop.someMailServer.com";

// Set the POP3 login/password.
mailman.PopUsername = @"***";
mailman.PopPassword = @"***";

// You may keep a list of already-seen UIDLs in a text file:
// If this is the first time you're running this example,
// create an empty text file named "seenUidls.txt"
CkoStringArray *saSeenUidls = [[CkoStringArray alloc] init];
BOOL success = [saSeenUidls LoadFromFile: @"seenUidls.txt"];
if (success != YES) {
    NSLog(@"%@",@"failed to load seenUidls.txt");
    return;
}

// Get the complete list of UIDLs on the mail server.
CkoStringArray *saUidls = [mailman GetUidls];
if (mailman.LastMethodSuccess == NO) {
    NSLog(@"%@",mailman.LastErrorText);
    return;
}

// Create a new string array object (it's an object, not an actual array)
// and add the UIDLs from saUidls that aren't already seen.
CkoStringArray *saUnseenUidls = [[CkoStringArray alloc] init];

int i = 0;
int n = [saUidls.Count intValue];
while (i < n) {
    if ([saSeenUidls Contains: [saUidls GetString: [NSNumber numberWithInt: i]]] != YES) {
        success = [saUnseenUidls Append: [saUidls GetString: [NSNumber numberWithInt: i]]];
    }

    i = i + 1;
}

if ([saUnseenUidls.Count intValue] == 0) {
    NSLog(@"%@",@"No unseen emails!");

    return;
}

// Download in full the unseen emails:
CkoEmailBundle *bundle = [mailman FetchMultiple: saUnseenUidls];
if (mailman.LastMethodSuccess == NO) {
    NSLog(@"%@",mailman.LastErrorText);

    return;
}

CkoEmail *email = 0;
i = 0;
while (i < [bundle.MessageCount intValue]) {
    email = [bundle GetEmail: [NSNumber numberWithInt: i]];
    NSLog(@"%@",email.From);
    NSLog(@"%@",email.Subject);
    NSLog(@"%@",@"----");

    i = i + 1;
}

// Save saUidls to "seenUidls.txt"
success = [saUidls SaveToFile: @"seenUidls.txt"];