E-mail marketing to a house list continues to be the top marketing channel for many industrial companies and manufacturers according to Trends in Industrial Marketing 2011 from GlobalSpec. However, that doesn’t necessarily mean that industrial marketers are very happy with the results. The biggest challenge in e-mail marketing faced by industrial marketers, besides not enough resources, is getting their subscribers to pay attention to their emails when everybody’s inboxes are already overflowing with messages. mail List Hygiene. Check any rented list against your house list.