The From Line

Incentives are a great way to motivate new signups - and they often work. However, using incentives for the sole purpose of growing your email list can lead to problems. The quality of these addresses will likely suffer since many use fake addresses just to get their hands on the incentive.

Those fake addresses (whether made up or belonging to someone else), will lead to high bounce rates, complaint rates and have a negative impact on your sender reputation. Before you know it, you have a major deliverability problem on your hands.