I know, I get ignored.
Look here:
https://www.diafaan.com/sms-tutorials/gsm-modem-tutorial/
This basically shows how to use a 3G modem to send SMS messages. The Motorola V3 is a 3G modem when you connect somthing through the USB port and the modem port has to be set to something in setup for it to work.
The 3g modem does't have to be a cell phone and only some will work. You can buy a 3G modem that either uses a serial or USB port.
You need a SIM card and a cell phone subscription.
If you can send an email and you know the carrier, you can send an SMS via the email system. It's like <phone number>@<carrier domain>.
The carrier may use a different domain for MMS messages and txt messages.
The problem becomes just how to send the email message directly. If this happens to be a home, you likely don;t have an MX (mail exchanger) record and a public IP addresss that doesn;t change, so you cant send email directly.
One of the questions was:
1) Do you expect to use a cellular modem?
2) Is this a domain that has an MX record and email server and do you have internet access?
I don;t have all of the answers, but those questions will help those that do.
At one point, I had access to a secure email server if I provided the right credentials, but I risked email being rejected because it came from an alternate domain.
Many API's (Application Programming Interfaces) in a lot of devices don't implement a secure email server and only allow port 25.
Your ISP doesn;t want a rogue program on your computer acting as an insecure mailer sending out SPAM.