Many years ago when I was still a rookie list broker, I received an enquiry from a car maker wanting to conduct a mail-out. One of the industries they included in their order was manufacturing.
What neither myself nor the client realised was that a small number of other car makers would be present through selecting manufacturing. Fast forward a few weeks and I received feedback from the client that they had mailed a number of people at one of their main rivals.
If you are a business to business marketer considering list rental, it's important to decide whether to exclude your competitors.
In the vast majority of cases our clients do exclude competitors due to not wanting to alert them to their offerings, realising they won't order from them, reduction in waste and avoiding any embarrassment.
Occasionally our client might have no issue including their competitors. Perhaps mind games are at play or there may be some difference in the services or products offered that would still see a competitor potentially order from them.
Either way make sure you are aware of the potential for competitors to be present and advise your broker if you'd like them excluded (especially if they are a rookie!).