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While there’s a growing volume of spam cluttering inboxes, email marketing and communication is still a highly effective tool for campaigns.

It has, however, become more difficult to reach voters through email. Still, those who can do it, and do it well, will be handsomely rewarded. In campaigns, the only email that really matters is the call to action (CTA). Here are a few pointers on how to make the most out of your CTA effort.

Subject Lines Are Everything

The success of all CTA campaigns is predicated on the subject line. If your subject line fails to connect, then the email is never opened, and subsequently no action is taken. A solid subject line must do two things. First, it must evoke an emotion powerful enough to compel the reader to open the email. Second, it should tell the reader exactly what the reader would find in the email. In other words, what the call to action is.

The first part is tricky the one. You can use fonts, exclamation marks, spaces and creative copy to make this happen. But don’t overdo it. Some of the more common tactics are creating a sense of urgency — the kids call it FOMO (fear of missing out) — and personalization.

These are all good, baseline, approaches to writing captivating subject lines, but they’re starting to get stale and losing their effectiveness. You should spend the majority of your time crafting and testing multiple subject lines. No silver bullet here.

Timing Is Key

Appropriate timing is a necessary component of a successful CTA campaign. There are two components to the timing factor: when is email usage at its peak and when is the subject matter of my email most relevant? The short and sweet answer to the first question is 10 a.m. on any weekday. If you have enough data on a particular list you’ve mailed in the past, you can segment users and designate send times based on individual’s historical performance.

If that sounds like too much work, there are a lot of agencies and third-party software programs that can do this for you. The second component is the more critical one. I like to follow traditional media outlet leads on this one. If Fox is building up a big hour-long spot about the Stand Your Ground law, then have an email mocked up and ready to go with a CTA about the Second Amendment that hits toward the end of the spot.

Don’t Get Greedy

Your CTA email should have a single call to action, not five. When you give the reader too many choices — click here to donate, make phone calls, host a party, sign the petition, volunteer, et cetera – more often than not they’ll choose not to choose.

This doesn’t mean you shouldn’t include your CTA several times in your email, because you most certainly should. But don’t lose the readers’ interest you worked so hard to get with your clever subject line and impeccable timing because you overwhelmed them with too many choices.

Maintain Your Creditability

The temptation to send, and send often, is always present. We tell ourselves it’s a simple math: the more we blast out, the more we get back. In practice, if the spam filters and the ISPs don’t get you, then the consumer certainly will punish you.

You will see open rates plummet, conversion rates fall off the map, and your list you paid good money for (or spent a lot of time cultivating) will dwindle. Your list is a tangible asset. If you abuse it, it will depreciate rapidly.

Finally, more important than consequences of running your list into the ground, it’s important to remember the effect your online actions have on your offline reputation. Pollsters are seeing a rise in the number of negative verbatim referencing “spam” mail.

Jessica Evers is the email manager for the Prosper Group and has worked on email campaigns for Mitt Romney, Allen West Foundation, and is currently helping to conduct email fundraising for Scott Walker’s presidential campaign. John is a digital communications strategist formerly with the Prosper Group.