The Canadian government's CASL (Canada Anti-Spam Legislation) has led to a growing trend where wireless carriers are blocking SMS traffic from long codes, which can prevent users from signing up and logging into applications. This issue affects companies using SMS for two-factor authentication logins or phone verification, particularly in Canada, where short codes are preferred over long codes due to increased filtering of A2P traffic. To address this issue, Twilio offers APIs that are pre-configured to comply with carrier policies, including Authy and Verify, which can help avoid blocking and ensure smooth user experience for applications using SMS for 2-factor authentication or phone verification.