compose: use email domain name in Message-Id

RFC 5322 recommends using a domain name on the right-hand side of the
"@" in Message-Ids.

Since the local host domain name cannot be obtained reliably, use the
sender email domain name by default. Add a new configuration option to
maintain the old behavior.

Link: https://www.rfc-editor.org/rfc/rfc5322.html#section-3.6.4
Signed-off-by: Adnan Maolood <adnan@maolood.com>
Acked-by: Robin Jarry <robin@jarry.cc>

1 files changed, 23 insertions, 1 deletions

diff --git a/widgets/compose.go b/widgets/compose.go
index f682fe5c..05d06a7f 100644
--- a/widgets/compose.go
+++ b/widgets/compose.go
@@ -136,6 +136,7 @@ func (c *Composer) SwitchAccount(newAcct *AccountView) error {
 	}
 	// ensure that from header is updated, so remove it
 	c.header.Del("from")
+	c.header.Del("message-id")
 	// update entire composer with new the account
 	if err := c.setupFor(newAcct); err != nil {
 		return err
@@ -845,10 +846,13 @@ func (c *Composer) PrepareHeader() (*mail.Header, error) {
 	// control headers not normally set by the user
 	// repeated calls to PrepareHeader should be a noop
 	if !c.header.Has("Message-Id") {
-		err := c.header.GenerateMessageID()
+		hostname, err := getMessageIdHostname(c)
 		if err != nil {
 			return nil, err
 		}
+		if err := c.header.GenerateMessageIDWithHostname(hostname); err != nil {
+			return nil, err
+		}
 	}
 
 	// update the "Date" header every time PrepareHeader is called
@@ -861,6 +865,21 @@ func (c *Composer) PrepareHeader() (*mail.Header, error) {
 	return c.header, nil
 }
 
+func getMessageIdHostname(c *Composer) (string, error) {
+	if c.acctConfig.SendWithHostname {
+		return os.Hostname()
+	}
+	addrs, err := c.header.AddressList("from")
+	if err != nil {
+		return "", err
+	}
+	_, domain, found := strings.Cut(addrs[0].Address, "@")
+	if !found {
+		return "", fmt.Errorf("Invalid address %q", addrs[0])
+	}
+	return domain, nil
+}
+
 func (c *Composer) parseEmbeddedHeader() (*mail.Header, error) {
 	_, err := c.email.Seek(0, io.SeekStart)
 	if err != nil {
@@ -1531,6 +1550,9 @@ func (he *headerEditor) storeValue() {
 	default:
 		he.header.SetText(he.name, val)
 	}
+	if strings.ToLower(he.name) == "from" {
+		he.header.Del("message-id")
+	}
 }
 
 func (he *headerEditor) Draw(ctx *ui.Context) {