We're running a trial with ClickSend. We're going to have to start charging our customers who use it though. We send up to 10k alarm notification emails per month from various HMIs to dozens of end users. Probably half of them are on AT&T. I have the HMI programmed to let them edit the on call roster with contact info and select their carrier and the HMI creates the "Mail To" string for them using a list of gateway suffixes, so it was easy for me to switch one of them to ClickSend by eliminating the suffix lookup and just replacing it with "@sms.clicksend.com"

As a bonus, Clicksend offers voice calling too, so I programmed our trial HMI to let the end user select SMS, Voice, or Both. To get Clicksend to convert the alarm message to a voice call, the suffix is "@voice.clicksend.com".

This will be handy for folks who need a phone to ring to wake them up in the middle of the night for an emergency, and might be something they won't feel so bad about paying for.

If we can get ten of our customers to pay an annual fee of around $150, we'll break even on our cost for the service and setup.

The only problem we have seen so far is that voice calls can be delayed during peak business hours, mainly with AT&T. Our worse case test so far experienced a delay of over an hour before the phone rang. The 2nd worst case was around 30 minutes. Usually the texts come through in under 60 seconds and the voice call within 3 minutes.