As you know, undelivered messages happen for many reasons. Most of the time it is because the number is invalid or a landline, or carrier filtering (Check out this article HERE for more info on how to avoid carrier filtering and HERE for more information about using secondary numbers).
Now, you can set up an auto-check for all undelivered messages. What this will do is when a message is marked as undelivered, we will automatically look up that number for you and mark it with the appropriate category (Invalid, landline, VOIP, or mobile). This helps save you credits in the long run!
Checking the phone number type will cost 1 credit, but in the future, if that contact is in a group that you want to send a message to (pretend we checked it previously and it was marked as a landline), we will automatically skip that contact and you will save 1 credit! You can also manually check your contacts at anytime! Check out the article HERE on how you can do that!
To set this up:
First, go to your contacts page.
Next, click the drop down menu next to the settings icon. and select "Automatically lookup undelivered Nos."
Next, a box will pop up. Click the box at the bottom of the screen and then click "save".
And that's it! Now anytime a message is marked "undelivered", we will automatically check the phone type and mark it with the appropriate icon. (Once a number is checked, it will not be checked again)