Microsoft unreachable over IPv6 from our office

Question

Microsoft unreachable over IPv6 from our office

Yvan Watchman 0

Hello,

We're trying to do our daily operations, however the last few weeks it seems you have blocked our IPv6 prefix from Azure, hotmail etc.

Prefix: 2a07:e345::/32

Please check this and let me know why it has been blocked.

Yvans-MacBook-Pro:~ yvanwatchman$ mtr --psize 1472 login.microsoftonline.com --report -c 4
Start: 2026-02-27T12:27:58+0100
HOST: Yvans-MacBook-Pro.local     Loss%   Snt   Last   Avg  Best  Wrst StDev
  1.|-- 2a07:e345:ff4a::1          0.0%     4    2.4   2.6   1.9   3.5   0.7
  2.|-- 2a07:e345:1:3004::163      0.0%     4    7.4  20.8   7.4  56.1  23.6
  3.|-- 2a07:e345:1:3004::1        0.0%     4    8.3  38.6   8.3 127.6  59.3
  4.|-- fsx-cr1.nkh.xyphen.it      0.0%     4    7.3  11.4   7.3  20.9   6.4
  5.|-- 2a00:a7c0:e20a:22::2       0.0%     4   12.0  32.2   7.0  97.9  43.9
  6.|-- 2a01:111:2000:1::33d6      0.0%     4   11.6  13.7  11.6  16.3   2.4
  7.|-- 2a01:111:2000:2:8000::162  0.0%     4   11.3  24.6   8.3  65.6  27.4
  8.|-- 2603:1060:1:12::f35d       0.0%     4   96.4  88.5  23.8 210.0  87.9
  9.|-- 2603:1060:1:10::f7d6      25.0%     4   79.4  49.1  30.0  79.4  26.5
 10.|-- 2a01:111:201:f200::2175   75.0%     4   94.9  94.9  94.9  94.9   0.0
 11.|-- 2a01:111:201:f200::17c2   50.0%     4   81.0  90.8  81.0 100.7  13.9
 12.|-- 2a01:111:2000:6::576d      0.0%     4   26.0  59.4  26.0  87.5  29.8
 13.|-- 2603:10a0:106:8104::3e     0.0%     4   23.4  27.1  22.5  38.6   7.7
 14.|-- 2603:10a0:106:8307::4a     0.0%     4   23.8  23.6  22.5  24.4   0.8
 15.|-- 2603:10a0:11c:5d5::        0.0%     4   24.2  24.7  23.5  26.7   1.4
 16.|-- ???                       100.0     4    0.0   0.0   0.0   0.0   0.0
Yvans-MacBook-Pro:~ yvanwatchman$

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1 answer

Your answer

Answer 1

Microsoft 365 currently supports inbound IPv6 connectivity for many scenarios, but outbound IPv6 connectivity from Microsoft 365 services is not yet supported. For hybrid or cross-premises scenarios, Microsoft explicitly requires IPv4 exposure of on-premises or partner environments.

The available documentation does not provide any mechanism to check or remove a block on a customer-owned IPv6 prefix at the Microsoft network edge, nor does it describe any policy for blocking specific external IPv6 prefixes to Microsoft 365 endpoints such as Azure or Outlook/Hotmail.

For environments that are IPv6-only or primarily IPv6 and need to reach Microsoft 365 reliably, the documented guidance is:

Ensure IPv4 connectivity is available from the network to Microsoft 365 endpoints (for example, dual-stack or NAT64/DNS64).
If running IPv6-only services that must access Microsoft 365, use dynamic IPv6/IPv4 transition mechanisms such as DNS64/NAT64 so that traffic can reach Microsoft 365 over IPv4 where required.
For hybrid Exchange or similar scenarios, expose the on-premises environment via IPv4, because outbound IPv6 from Microsoft 365 to on-premises is not supported.

Given the constraints in the documentation, the supported path to restore reliable access is to:

Verify that the office network has working IPv4 egress to Microsoft 365 URLs and IP ranges.
If the network is IPv6-only, deploy DNS64/NAT64 or equivalent so that Microsoft 365 endpoints can be reached over IPv4.

Any investigation of a potential block on a specific IPv6 prefix (such as 2a07:e345::/32) would need to be handled directly by Microsoft support using internal tools that are not documented here.

References: