Network Implementation Guide › Troubleshooting › POP3 Email Blocking

POP3 Email Blocking

When the NBA blocks a POP3 email, the user experience is unusual and requires explanation. This unusual user experience is caused by the method used by POP3 clients (such as Outlook Express) to read emails from the server.

Under the POP3 email blocking scheme on the NBA, the NBA first blocks a mail by killing the session. Then, in a later session, it blanks out all blocked emails. The POP3 client does not see a successful mail retrieval until each blocked email is fetched as a blanked email.

What does the user see?

1. When the POP3 client first tries to retrieve emails from the server and one of the emails is blocked, the user sees an unexpected termination error message.

   This message indicates that the server has unexpectedly terminated the session.

2. During the subsequent email retrieval, the user sees an advisory message for the email that was previously blocked.
3. If a further email must be blocked, the user then sees another unexpected termination error message.
4. During the subsequent email retrieval, the user sees an advisory message for the email that was previously blocked.
5. This sequence repeats for each attempt to retrieve emails until there are no more emails that need to be blocked.