Office 365 can't connect to on-premises environment through IPv6

Applies To
Exchange Online via Office 365 E Plans Exchange Online via Office 365 P Plans Microsoft Exchange Online Dedicated Exchange Online Exchange Outlook

Symptoms

If your on-premises environment is exposed only through Internet Protocol Version 6 (IPv6), you may experience connectivity issues, such as the following:

  • You can't migrate on-premises mailboxes to Microsoft Exchange Online.
  • Exchange Online can't resolve availability lookups (free/busy) for on-premises users in your hybrid configuration.

Cause

This issue occurs because outbound IPv6 connectivity is not supported at this time.

Note Microsoft Office 365 currently supports inbound IPv6 connectivity, and plans exist to support outbound IPv6 connectivity.

Resolution

Expose your on-premises environment through IPv4.