TextMagic

TextMagic covers two-way texting, contact lists, and basic autoresponders, built by a company that's been in the SMS business since before smartphones existed and has stuck close to that core product rather than expanding heavily into email or push. It's used by roughly 25,000 business customers sending a combined 200 million texts a year, according to the company's own figures.

There's no monthly subscription: pricing is purely pay-as-you-go, around $0.049 per two-way SMS in the US, with credits purchased upfront and drawn down as you send. A toll-free number needed for two-way messaging adds a separate $10 monthly fee. A bring-your-own-carrier option lets you connect an existing Twilio or Vonage number and send through TextMagic's interface at roughly $0.01 per SMS, a meaningful discount over the standard rate if you already have carrier accounts elsewhere. It fits a business that sends in bursts rather than a steady monthly volume and doesn't want to pay for a subscription tier sized for a busier month.