Will Kelly argues text messages get roughly 80% open rates versus much lower email performance. He recommends using SMS for sales and email for information, with one promotional offer every four weeks to avoid annoying subscribers.
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If your current CRM can't send text messages, that's worth switching over in itself because email and text do not perform anywhere close to each other. Text messages get opened around 80% of the time, where email doesn't even come close to that. When money is on the line, you're trying to drive an actual sale, you send the text, save email for the stuff that's just informational. Keep the cadence simple. One offer once every 4 weeks. Not every week, not randomly, whenever it crosses your mind. Once every 4 weeks, like clockwork. So your list expects to hear from you instead of feeling spammed by you.