Increase max local-part length to 128

- Improves compatibility with Mailgun
- Closes #41
- Update CHANGELOG

smtpd/utils.go

@@ -182,8 +182,8 @@ LOOP:
 				inCharQuote = false
 			} else {
 				// End of local-part
-				if i > 63 {
-					return "", "", fmt.Errorf("Local part must not exceed 64 characters")
+				if i > 128 {
+					return "", "", fmt.Errorf("Local part must not exceed 128 characters")
 				}
 				if prev == '.' {
 					return "", "", fmt.Errorf("Local part cannot end with a period")

smtpd/utils_test.go

@@ -99,7 +99,8 @@ func TestValidateLocal(t *testing.T) {
 	}{
 		{"", false, "Empty local is not valid"},
 		{"a", true, "Single letter should be fine"},
-		{strings.Repeat("a", 65), false, "Only valid up to 64 characters"},
+		{strings.Repeat("a", 128), true, "Valid up to 128 characters"},
+		{strings.Repeat("a", 129), false, "Only valid up to 128 characters"},
 		{"FirstLast", true, "Mixed case permitted"},
 		{"user123", true, "Numbers permitted"},
 		{"a!#$%&'*+-/=?^_`{|}~", true, "Any of !#$%&'*+-/=?^_`{|}~ are permitted"},