Here are the frequently asked questions about HES support for IPv6:

• Does HES support IPv6?
  HES currently does not support IPV6 feature.
• If the mail server has IPv6 address, will it deliver the emails?
  If the server is dual stack and sending mails with IPv4, mail delivery will be okay.
• If the customer wants to approve/block certain IPv6 addresses in IP reputation services, will HES work on IPv6 sources?
  No. This is not yet supported.
• Will Mail Tracking and logs work and be displayed correctly?
  HES Mail Tracking and other logs currently do not support IPv6 display.
• Is it possible to modify the MX record to point to AAAA?
  It is possible if we start to support IPv6 and then we will need to point to AAAA.
• What happens if HES receives an email from an IPv6 source?
  The upstream IPv6 MTA cannot connect to HES, so HES will not accept the emails without any return/error code. In addition, the spam and anti-malware filters and policies will not be executed.