The telco carriers are cracking down on spam and unwanted texts by catching and dubious-looking texts in their spam filters. No one knows exactly how these spam filters work (that would defeat the purpose!), but there are a number of things you can do to increase the response rates of your texts and avoid the spam filters:
1) Keep texts as short as possible - ideally less than 240 characters. The shorter the text = the higher the response rate
2) Avoid using ALL CAPS and special characters such as $%#@/*
3) Keep URL links as short as possible and include no more than 1 in any text template
4) Avoid the use of free URL shorteners such as bit.ly and goo.gl (spammers are known to use these free tools a lot)
5) Always make sure the message is relevant and appropriate. Use 'FirstName' or 'LastName' fields to make them more personalized.
Additionally, there is no need to include a phone number for candidates to reach you (that's what call forwarding is for!)