As a user of Aevent, you'll most likely be wanting to use Twilio to send sms and/or mms.
In order to avoid service interruptions with Twilio, they have made it compulsory to register for the new protocol.
What is A2p-10DLC?
https://support.twilio.com/hc/en-us/articles/1260800720410-What-is-A2P-10DLC-
How to register:
https://www.twilio.com/docs/sms/a2p-10dlc/onboarding
Here are 2 simple answers to the Sample Message question:
Sample Message 1:
Congratulations (FIRSTNAME), Your registered for our Webinar on October 5th at 6pm EST! Your join link is (LINK)
Sample Message 2:
(FIRSTNAME), You missed our webinar yesterday, I just posted a replay of it, and you can access that here (LINK).