Use our Inactive Soft Bounce feature. This can be found under Contacts > Other Lists > Bounces & Opt-Outs. Hover over your Soft Bounce List, select 'Move to inactive soft bounces after...' and set this to 3-5. What this does is it prevents Act-On from mailing to contacts who soft bounce X many times in a row indefinitely. Continuously mailing to soft bounces is a huge detriment to your sender reputation as it reflect poor sending habits and bad list acquisition.