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.
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 ip4:220.127.116.11/15 ip4:18.104.22.168/16 ip4:22.214.171.124/14 ip4:126.96.36.199/17 ip6:2a01:111:f400::/48 ip6:2a01:111:f403::/48 -all"