i just would like to make you aware about a badly interpretation or missuse of mail loadbalancing from Microsoft side.
Microsoft is offering to its outlook.com clients a protecttion mechanism which is also used for loadbalancing when sending.
This results in the behaviour that every email delivery attempt will come from a new IP.
Which means that email can never be delivered to you, because the subnet they are using has a lot of hosts, see below.
Only chance to get rid of hanging mail attempts is to whitelist outlook.com.
below a query for a real domain. I have changed the real domainname to domain.com as i didnt want to pinpoint to somebody.
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Code: Select all
>set querytype=MX
> domain.com
Server: 10.213.213.244
Address: 10.213.213.244#53
Non-authoritative answer:
domain.com mail exchanger = 0 domain-com.mail.protection.outlook.com.
> set querytype=TXT
> domain.com
Server: 10.213.213.244
Address: 10.213.213.244#53
Non-authoritative answer:
domain.com text = "v=spf1 include:spf.protection.outlook.com -all"
domain.com text = "MS=ms46586979"
> spf.protection.outlook.com
Server: 10.213.213.244
Address: 10.213.213.244#53
Non-authoritative answer:
spf.protection.outlook.com text = "v=spf1 ip4:40.92.0.0/15 ip4:40.107.0.0/16 ip4:52.100.0.0/14 ip4:104.47.0.0/17 ip6:2a01:111:f400::/48 ip6:2a01:111:f403::/48 -all"