Hello,

I've verified that both Rebex POP3 and MailBee POP3 components behave the same. When the entire message is downloaded, it won't appear in the message list the next time.

That occurs when using e.g. Rebex GetMailMessage method (or MailBee DownloadEntireMessage method).

Simply:

• when you retrieve just the message headers from Gmail using POP3, messages are provided again each time you retrieve the message list
• when you retrieve a message using the GetMailMessage method, the message is marked in Gmail internally as "already received by POP3" and it is not accessible by POP3 connection any more (until the received flag is reset through web settings page).

NOTE: the behavior described only applies if the POP3 session is properly disconnected (by calling Disconnect method on the POP3 instance - calling the Dispose method only is not enough).

Here are two samples (using Rebex and MailBee components) that do the same. Both are retrieving the POP3 messages just one time.

Sample using Rebex Pop3 component:

Pop3 client = new Pop3(); 
client.Connect("pop.gmail.com", Pop3.DefaultImplicitSslPort, null, Pop3Security.Implicit);
client.Login("username", "password");

Pop3MessageCollection messages = client.GetMessageList(Pop3ListFields.FullHeaders); 
foreach (Pop3MessageInfo msg in messages)
{
    // IF THE FOLLOWING LINE IS USED, THE MESSAGE WON'T APPEAR WHEN GETTING THE LIST NEXT TIME 
    // (equivalent to MailBee Pop3.DownloadEntireMessage method)
    MailMessage fullMsg = client.GetMailMessage(msg.SequenceNumber);

    Console.WriteLine("From: " + msg.From + ", To: " + msg.To + ", Subject: " + msg.Subject);
}

client.Disconnect();

Sample using MailBee Pop3 component:

Pop3 pop = new Pop3();
pop.Connect("pop.gmail.com", 995);
pop.SslMode = MailBee.Security.SslStartupMode.OnConnect;
pop.Login("username", "password");

MailMessageCollection msgs = pop.DownloadMessageHeaders();
foreach (MailMessage msg in msgs)
{
    // IF THE FOLLOWING LINE IS USED, THE MESSAGE WON'T APPEAR WHEN GETTING THE LIST NEXT TIME 
    // (equivalent to Rebex Pop3.GetMailMessage method)
    MailMessage fullMsg = pop.DownloadEntireMessage(msg.IndexOnServer);

    Console.WriteLine("From: " + msg.From.Email + ", To: " + msg.To.AsString + ", Subject: " + msg.Subject);                
}

pop.Disconnect();

NOTE: The behavior mentioned in this post is specific for the Gmail POP3 communication. Other POP3 server would behave another way.

Hello,

it looks like your GMail account is configured to sends only fresh messages via POP3 protocol. You might need to reconfigure it. To do so:

• click on "Settings" link (top, right of the gmail page)
• click on "Forwarding and POP/IMAP" tab
• select "Enable POP for all mail (even mail that's already been downloaded)"
• click "Save changes"

This should help. Alternatively you can try IMAP for accessing your GMail mailbox. It will enable you to access all your emails and not only messages in the inbox.