I've heard from a few people who work in politics in state and national congresses that (non-form) physical letters and phone calls from concerned constituents can have a surprising amount of weight on the decisions of congresspeople. I imagine it's less true for form emails like this, but still probably worth a go.
I think the basic way to judge this is "Is this a signal that the person who sent it is motivated to pay attention and vote based on this?"
Congresscritters care most about votes. They'll take campaign donations if thats all they can get, but they then need to figure out how to turn those campaign donations into votes.
