Indeed, I'm running PHP 7, so that's part of the problem; PHP newer than 5.6.7 recognizes Swift Mailer's STREAM_CRYPTO_METHOD_TLS_CLIENT specifically as STREAM_CRYPTO_METHOD_TLSv1_0_CLIENT. In fact, if I were to disable TLS 1.0 connections on the server level and left StreamBuffer.php file in...
I second this. I use SMTP with SparkPost, too, and this is a real problem. Swift Mailer seems to be defaulting to TLS 1.0, even though my server supports TLS 1.1 and 1.2 as well. SparkPost is refusing anything lower than 1.1. I came up with a tentative fix by altering...