1a=model number sort ascending
1d=model number sort descending
2a=name sort ascending
2d=name sort descending
4a=price sort ascending
4d=price sort descending

# Since v2.10.9 you can define the email validation level. Possible values are:
# 0 = Disable email address validation.
# 1 = TLD & domain validation + no local part validation
# 2 = RFC821 email validation without escaping and quoting of local part
# 3 = RFC821 email validation [default value if this setting is undefined]
define(“EMAIL_ADDRESS_VALIDATION_LEVEL”,3);

In file:
admin/commonlib/lib/userlib.php
There are some lists of what are deemed valid domains…
See lines 497 and 518. You can add new TLDs that will then pass validation.