Mark Brownlow has a great article up about how senders can stop subscribers from regretting they signed up for mail. He starts off saying
So how to avoid subscriber’s remorse?
The obvious one – and stop me if you’re heard this before – is sending relevant, timely, useful emails. Unfortunately, remorse can set in long before you have the chance to establish your value through your future emails. So your “remorse reduction strategy” needs to begin before the subscriber has even opted-in.
He lists a number of strategies to minimize subscribers hitting the this is spam button because they did not get the mail they were expecting from a sender.