You may have received the following email:
Your org has been identified as having users or integrations still connecting to Salesforce using TLS 1.0 encryption protocol.
You are wondering if Heroku Connect is a contributing factor.
Heroku Connect is fully compatible with TLS 1.2+.
Heroku does not support SSLv3, TLS 1.0, or TLS 1.1 for security reasons. Heroku curates the cipher suites to strike a balance between security best practices and backward compatibility.