eNewsletter Pro Enterprise Edition has full support for bounced email tracking.  There are several ways in which an email message can bounce

Undeliverable Messages

• When the mail server receives a positive response indicating that delivery is not possible. i.e. A user does not exist on the mail server for the domain or no mail servers are listed for the domain. 
• When the recipients mail server is currently down for one reason or another.  Cases such as this may not be a true bounce.

Returned Messages

• Mail server accepts the message but later rejects it for one reason or another.

For Undeliverable Messages the mail server will place these messages in the \failed\ folder.  For example, C:\Program Files\eNewsletterPro\Failed\

The eNewsletter Pro Bounce Engine scans this folder every 8 minutes (by default).  Email addresses are extracted from these failed messages and logged as a bounced address.  The failed message is then deleted to preserve space.  You can change the frequency with which bounced addresses are filtered by changing the eNewsletter Pro Bounce Engine schedule under Scheduled Tasks in the Windows control panel.

If the receiving mail server initially accepts the message then later rejects/returns it, the message is returned to the bounced email address that was defined in the Administrative Setup.  This email address is the same for all users.  This email account must be a POP3 compliant address.  The eNewsletter Pro Bounce Engine checks this POP3 email account for returned messages after emptying the \failed\ folder.  This task repeats every 8 minutes.

What happens to bounced addresses? 

Each time the eNewsletter Pro Bounce Engine finds a bounced address, it simply increases the Bounce counter in the database for that specific email address.  The email address is NOT automatically removed from the database.

How do I remove Bounced Addresses?

To remove bounced addresses, use the Filter Bounces tool in the user administration console.  This tool allows you to remove all addresses that have bounced X number of times.  It is recommended that you delete an address only after it has bounced several times.  If the recipient mail server is down when attempting to deliver the message, the address is erroneously labeled as a bounce when in fact the address may be valid.