Shop Talk: Opt-Out Email Strategies

Besides getting your IP blocked, customers may decide your use of their email addresses is unwarranted and stop doing business with you.

Also, consider how long it's been since your company sent to these email addresses. Abandoned email addresses are often re-used by email providers as decoy accounts (commonly referred to as spam traps) to catch spammers. Besides spam traps, ISPs and email receivers will also determine whether to accept your email based on the number of bad or nonexistent addresses you mail to.