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 go-gitea#17477

Signed-off-by: Andrew Thornton <[email protected]>

Author: zeripath

custom/conf/app.example.ini

@@ -1450,6 +1450,10 @@ PATH =
 ;; Mail from address, RFC 5322. This can be just an email address, or the `"Name" <[email protected]>` format
 ;FROM =
 ;;
+;; Sometimes it is helpful to use a different address on the envelope. Set USE_DIFFERENT_ENVELOPE_FROM to true to use ENVELOPE_FROM as the from on the envelope
+;USE_DIFFERENT_ENVELOPE_FROM=false
+;ENVELOPE_FROM =
+;;
 ;; Mailer user name and password
 ;; Please Note: Authentication is only supported when the SMTP server communication is encrypted with TLS (this can be via STARTTLS) or `HOST=localhost`.
 ;USER =

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -598,6 +598,8 @@ Define allowed algorithms and their minimum key length (use -1 to disable a type
   - Otherwise if `IS_TLS_ENABLED=false` and the server supports `STARTTLS` this will be used. Thus if `STARTTLS` is preferred you should set `IS_TLS_ENABLED=false`.
 - `FROM`: **\<empty\>**: Mail from address, RFC 5322. This can be just an email address, or
    the "Name" \<[email protected]\> format.
+- `USE_DIFFERENT_ENVELOPE_FROM`: **false**: Set to **true** to use the value of `ENVELOPE_FROM` as the From address on the SMTP mail envelope.
+- `ENVELOPE_FROM`: **\<empty\>**: Address set as the From address on the SMTP mail envelope if `USE_DIFFERENT_ENVELOPE_FROM` is set to true.
 - `USER`: **\<empty\>**: Username of mailing user (usually the sender's e-mail address).
 - `PASSWD`: **\<empty\>**: Password of mailing user.  Use \`your password\` for quoting if you use special characters in the password.
    - Please note: authentication is only supported when the SMTP server communication is encrypted with TLS (this can be via `STARTTLS`) or `HOST=localhost`. See [Email Setup]({{< relref "doc/usage/email-setup.en-us.md" >}}) for more information.

modules/setting/mailer.go

@@ -16,13 +16,15 @@ import (
 // Mailer represents mail service.
 type Mailer struct {
 	// Mailer
-	Name            string
-	From            string
-	FromName        string
-	FromEmail       string
-	SendAsPlainText bool
-	MailerType      string
-	SubjectPrefix   string
+	Name                     string
+	From                     string
+	EnvelopeFrom             string
+	UseDifferentEnvelopeFrom bool
+	FromName                 string
+	FromEmail                string
+	SendAsPlainText          bool
+	MailerType               string
+	SubjectPrefix            string
 
 	// SMTP sender
 	Host              string
@@ -73,6 +75,8 @@ func newMailService() {
 		SendmailTimeout: sec.Key("SENDMAIL_TIMEOUT").MustDuration(5 * time.Minute),
 	}
 	MailService.From = sec.Key("FROM").MustString(MailService.User)
+	MailService.UseDifferentEnvelopeFrom = sec.Key("USE_DIFFERENT_ENVELOPE_FROM").MustBool()
+	MailService.EnvelopeFrom = sec.Key("ENVELOPE_FROM").MustString("")
 
 	if sec.HasKey("ENABLE_HTML_ALTERNATIVE") {
 		log.Warn("ENABLE_HTML_ALTERNATIVE is deprecated, use SEND_AS_PLAIN_TEXT")

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.UseDifferentEnvelopeFrom {
+		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.UseDifferentEnvelopeFrom {
+		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)