What Happens to Bad Mail Addresses?

If ListManager is unable to send mail to an address after all its retry attempts it increments the person's bounce (permanent failure) count by one. Once the number reaches the value set in the List Settings screen, then that person is put on hold and mail will not be sent to them until they are unheld. Depending on how your list is set up, held users may or may not be deleted after a specified length of time. You also have the option of periodically notifying users who are on hold to give them the opportunity to unhold themselves. See Utilities: List Settings.

Often, email addresses are not permanently bad. For example, addresses sometime exceed their mailbox size and cannot receive mail. But, when the user clears their mailbox, they are able to receive mail again. This results in a transient failure while ListManager retries to send the mailing. Therefore, they may not reach the number of permanent failures to be put on hold. This is the reason why ListManager may take several days of transient failures before holding people since many mail problems are temporary. For detailed information on how to configure the handling of error mail, see Utilities: List Settings: Automatic Maintenance: Error Mail.