> On 16 Jan 2018, at 10:49, jin&hitman&Barracuda <jinhit...@gmail.com> wrote: > > We are having difficulties while delivering mails to Microsoft's domains like > hotmail and outlook.
They appear to have a DNS problem which is causing outbound mail to fail. Their SMTP servers are using non-existent hostnames when they say HELO. This DNS brokenness may well be wreaking havoc for those using SPF, DKIM, etc when speaking to M$ mail servers or receiving email from them.