fix: include missing mail headers (resolve #472)

models/mail_address.go

@@ -1,6 +1,9 @@
 package models
 
-import "regexp"
+import (
+	"regexp"
+	"strings"
+)
 
 const (
 	MailPattern      = "[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\\.[a-zA-Z0-9-.]+"
@@ -36,6 +39,14 @@ func (m MailAddress) Raw() string {
 	return ""
 }
 
+func (m MailAddress) Domain() string {
+	split := strings.Split(m.Raw(), "@")
+	if len(split) != 2 {
+		return ""
+	}
+	return split[1]
+}
+
 func (m MailAddress) Valid() bool {
 	return emailAddrRegex.Match([]byte(m))
 }