upgrade deps; rewrite smtp session

vendor/github.com/emersion/go-smtp/smtp.go

@@ -2,29 +2,93 @@
 //
 // It also implements the following extensions:
 //
-//  8BITMIME: RFC 1652
-//  AUTH: RFC 2554
-//  STARTTLS: RFC 3207
-//  ENHANCEDSTATUSCODES: RFC 2034
-//  SMTPUTF8: RFC 6531
-//  REQUIRETLS: RFC 8689
-//  CHUNKING: RFC 3030
-//  BINARYMIME: RFC 3030
+//   - 8BITMIME (RFC 1652)
+//   - AUTH (RFC 2554)
+//   - STARTTLS (RFC 3207)
+//   - ENHANCEDSTATUSCODES (RFC 2034)
+//   - SMTPUTF8 (RFC 6531)
+//   - REQUIRETLS (RFC 8689)
+//   - CHUNKING (RFC 3030)
+//   - BINARYMIME (RFC 3030)
+//   - DSN (RFC 3461, RFC 6533)
 //
 // LMTP (RFC 2033) is also supported.
 //
 // Additional extensions may be handled by other packages.
 package smtp
 
-import (
-	"errors"
-	"strings"
+type BodyType string
+
+const (
+	Body7Bit       BodyType = "7BIT"
+	Body8BitMIME   BodyType = "8BITMIME"
+	BodyBinaryMIME BodyType = "BINARYMIME"
 )
 
-// validateLine checks to see if a line has CR or LF as per RFC 5321
-func validateLine(line string) error {
-	if strings.ContainsAny(line, "\n\r") {
-		return errors.New("smtp: A line must not contain CR or LF")
-	}
-	return nil
+type DSNReturn string
+
+const (
+	DSNReturnFull    DSNReturn = "FULL"
+	DSNReturnHeaders DSNReturn = "HDRS"
+)
+
+// MailOptions contains parameters for the MAIL command.
+type MailOptions struct {
+	// Value of BODY= argument, 7BIT, 8BITMIME or BINARYMIME.
+	Body BodyType
+
+	// Size of the body. Can be 0 if not specified by client.
+	Size int64
+
+	// TLS is required for the message transmission.
+	//
+	// The message should be rejected if it can't be transmitted
+	// with TLS.
+	RequireTLS bool
+
+	// The message envelope or message header contains UTF-8-encoded strings.
+	// This flag is set by SMTPUTF8-aware (RFC 6531) client.
+	UTF8 bool
+
+	// Value of RET= argument, FULL or HDRS.
+	Return DSNReturn
+
+	// Envelope identifier set by the client.
+	EnvelopeID string
+
+	// The authorization identity asserted by the message sender in decoded
+	// form with angle brackets stripped.
+	//
+	// nil value indicates missing AUTH, non-nil empty string indicates
+	// AUTH=<>.
+	//
+	// Defined in RFC 4954.
+	Auth *string
+}
+
+type DSNNotify string
+
+const (
+	DSNNotifyNever   DSNNotify = "NEVER"
+	DSNNotifyDelayed DSNNotify = "DELAY"
+	DSNNotifyFailure DSNNotify = "FAILURE"
+	DSNNotifySuccess DSNNotify = "SUCCESS"
+)
+
+type DSNAddressType string
+
+const (
+	DSNAddressTypeRFC822 DSNAddressType = "RFC822"
+	DSNAddressTypeUTF8   DSNAddressType = "UTF-8"
+)
+
+// RcptOptions contains parameters for the RCPT command.
+type RcptOptions struct {
+	// Value of NOTIFY= argument, NEVER or a combination of either of
+	// DELAY, FAILURE, SUCCESS.
+	Notify []DSNNotify
+
+	// Original recipient set by client.
+	OriginalRecipientType DSNAddressType
+	OriginalRecipient     string
 }