On Thu, 10 Feb 2022, Tim Bray via mailop wrote:
Hi,
Is anybody else having trouble relaying email out of office365.
I think they have broken their reverse DNS.
Our method to trust
*.outbound.protection.outlook.com
2022-02-10 09:51:46 H=(GBR01-LO2-obe.outbound.protection.outlook.com)
[2a01:111:f400:7e15::200]
When we receive from 2a01:111:f400:7e15::200 this reverse lookups to
mail-lo2gbr01lp20200.outbound.protection.outlook.com.
but when you forward check
mail-lo2gbr01lp20200.outbound.protection.outlook.com. it resolves to ::1
Which is when I think exim goes `I'll ignore than DNS record`
I'm just interested if anybody has the same problem. A new problem that
started sometime since 2022-02-09 20:39:38 UTC. (our users don't send much
email over night in UK time.
I can confirm that there's something weird with their DNS with IPv6.
$ dig +short GBR01-LO2-obe.outbound.protection.outlook.com AAAA
2a01:111:f400:7e15::200
$ dig +short -x 2a01:111:f400:7e15::200
mail-lo2gbr01lp20200.outbound.protection.outlook.com.
$dig +short mail-lo2gbr01lp20200.outbound.protection.outlook.com AAAA
::1
Using A (IPv4) records there's no issue.
Cheers.
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