When a domain MX host only have AAAA record but no A record, then the domain is considered as invalid and user cannot create account / log in.

Expected behaviour

domain with IPv6 only MX should be considered as valid.

Actual behaviour

domain is considered as invalid. User cannot create account.

Steps to reproduce the problem

Try to create an account using a domain for which only IPv6 MX exists

Specifications

Found using 2.7.1 stable release.