If you really want to know that your SMS reached its destination, you can activate a delivery report. It will show you if the SMS is delivered and even when it was read.

Android 9
Step 1:  Open  Messages
Step 2:  Open the  menu
Step 3:  Open the  settings
Step 4:  Tap on  Advanced
Step 5:  Activate or deactivate  SMS delivery reports
  1. Open Messages
  2. Open the menu
  3. Open the settings
  4. Tap on Advanced
  5. Activate or deactivate SMS delivery reports

Android Instructions
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