Add settings to allow different SMTP envelope from address (#17479)

* Add settings to allow different SMTP envelope from address

Sometimes it may be advisable to hide or alias the from address on an SMTP mail
envelope. This PR adds two new options to the mailer to allow setting of an overriding
from address.

Fix #17477

Signed-off-by: Andrew Thornton <art27@cantab.net>

services/mailer/mailer.go

@@ -210,8 +210,14 @@ func (s *smtpSender) Send(from string, to []string, msg io.WriterTo) error {
 		}
 	}
 
-	if err = client.Mail(from); err != nil {
-		return fmt.Errorf("Mail: %v", err)
+	if opts.OverrideEnvelopeFrom {
+		if err = client.Mail(opts.EnvelopeFrom); err != nil {
+			return fmt.Errorf("Mail: %v", err)
+		}
+	} else {
+		if err = client.Mail(from); err != nil {
+			return fmt.Errorf("Mail: %v", err)
+		}
 	}
 
 	for _, rec := range to {
@@ -242,7 +248,12 @@ func (s *sendmailSender) Send(from string, to []string, msg io.WriterTo) error {
 	var closeError error
 	var waitError error
 
-	args := []string{"-f", from, "-i"}
+	envelopeFrom := from
+	if setting.MailService.OverrideEnvelopeFrom {
+		envelopeFrom = setting.MailService.EnvelopeFrom
+	}
+
+	args := []string{"-f", envelopeFrom, "-i"}
 	args = append(args, setting.MailService.SendmailArgs...)
 	args = append(args, to...)
 	log.Trace("Sending with: %s %v", setting.MailService.SendmailPath, args)