Code is quite simple:
using(Pop3 pop3 = new Pop3())
pop3.Connect("pop3.server.com"); // or ConnectSSL for SSL
List<string> uids = pop3.GetAll();
foreach (string uid in uids)
var eml = pop3.GetMessageByUID(uid);
IMail email = new MailBuilder().CreateFromEml(eml);
string subject = email.Subject;
Now, depending on your server and your server configuration, not all emails might be returned.
For example in Gmail, you can enable POP3 for all messages -or- only for mail that arrives from now on.
Take a look at Gmail's POP3 behavior here:
Some servers may limit the amount of messages they return.
Consider using IMAP protocol, IMAP is usually not affected by such limits.