Adding upstream version 3.6.2.

Signed-off-by: Daniel Baumann <daniel@debian.org>

sender_starttls.go

@@ -0,0 +1,47 @@
+package mailyak
+
+import (
+	"bytes"
+	"net"
+)
+
+// senderWithStartTLS connects to the remote SMTP server, upgrades the
+// connection using STARTTLS if available, and sends the email.
+type senderWithStartTLS struct {
+	hostAndPort string
+	hostname    string
+	buf         *bytes.Buffer
+}
+
+func (s *senderWithStartTLS) Send(m sendableMail) error {
+	conn, err := net.Dial("tcp", s.hostAndPort)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = conn.Close() }()
+
+	return smtpExchange(m, conn, s.hostname, true)
+}
+
+func newSenderWithStartTLS(hostAndPort string) *senderWithStartTLS {
+	hostName, _, err := net.SplitHostPort(hostAndPort)
+	if err != nil {
+		// Really this should be an error, but we can't return it from the New()
+		// constructor without breaking compatability. Fortunately by the time
+		// it gets to the dial() the user will get a pretty clear error as this
+		// hostAndPort value is almost certainly invalid.
+		//
+		// This hostname must be split from the port so the correct value is
+		// used when performing the SMTP AUTH as the Go SMTP implementation
+		// refuses to send credentials over non-localhost plaintext connections,
+		// and including the port messes this check up (and is probably the
+		// wrong thing to be sending anyway).
+		hostName = hostAndPort
+	}
+
+	return &senderWithStartTLS{
+		hostAndPort: hostAndPort,
+		hostname:    hostName,
+		buf:         &bytes.Buffer{},
+	}
+}