Knowledgebase

You must maintain your lists so minimum bounces occur.  Bounces are bad for many reasons:

  Sending to an invalid email address hurts the IP reputation of the servers and can affect deliverabilty of other emails.

  Bounces cause extra server load in generating the bounces and/or delivering the bounces.

  Bounces fill up mail boxes.  Each email is a file.  If you have 50,000 bounces in an email account
    it makes it almost impossible to maintain
    backups take a lot longer incurring extra server load
    delivering addtional email to the a mailox with large numbers of email in it causes extra server load that increases as the mailbox grows

The bounce rate should be less than 1%.  Failure to maintain a clean list, large email boxes of unread emails, etc may result in site suspension, daily backup exclusion, etc for excessive resource usage.