Add support for no-auth SMTPs

config.toml.sample

@@ -79,7 +79,7 @@ max_idle = 10
         host = "my.smtp.server"
         port = "25"
 
-        # cram or plain.
+        # cram | plain | empty for no auth
         auth_protocol = "cram"
         username = "xxxxx"
         password = ""

messenger/emailer.go

@@ -43,7 +43,7 @@ func NewEmailer(srv ...Server) (Messenger, error) {
 		var auth smtp.Auth
 		if s.AuthProtocol == "cram" {
 			auth = smtp.CRAMMD5Auth(s.Username, s.Password)
-		} else {
+		} else if s.AuthProtocol == "plain" {
 			auth = smtp.PlainAuth("", s.Username, s.Password, s.Host)
 		}