Email hygiene credits can be used with List Cleanings or ReachMail's Signup Shield technology. Purchase email hygiene credits by going to your Account tab and using the Buy button on the amount of credits you would like to purchase. Credits are purchasable in 1,000, 10,000, 100,000, and 1,000,000 blocks.
Any unused credits will rollover month-to-month and 2 years from the date of purchase. Any free promotional credits given expire after 1 year.