Mailer UseTLS SERVER_SMTP_USE_TLS Deprecation

With the recent update to mailer, the option UseTLS (Env: SERVER_SMTP_USE_TLS) was deprecated in favour of the option Encryption (Env: SERVER_SMTP_ENCRYPTION). If you were using the SERVER_SMTP_USE_TLS flag before to enable TLS, you'll need to migrate to the SERVER_SMTP_ENCRYPTION setting of tls. For the moment, both settings are supported (with a warning being printed when using SERVER_SMTP_USE_TLS, however support for the deprecated config will be dropped in one of the next releases.