We divide our contacts into product categories. Some contacts get emailed multiple times a year while others maybe once. When we haven't sent to a category in a long time or have a major announcement we will send our contact list to our regional sales managers. We instruct them to tell us if they think we are missing a customer/company or a specific contact at a company. This helps us add contacts we weren't told about for various reasons (mostly, the salesmen forget to tell us.)   End of the year we usually send a Thanksgiving email and Xmas/New years email to all our contacts. This is a great time to see what contacts are still valid and clean up from there.   Throughout the year, I will wait 3-6 months to delete "Suspended" contacts; or see if the next 2-3 emails sent to them still come back as "Suspended".  ... View more