Hi, I wonder if there's anyone from Microsoft out there that can advise bout some bounces we're seeing.
Since yesterday, we started receiving bounces from protection.outlook.com when attempting delivery to hotmail.co.uk and live.co.uk. There's an assorted collection of responses but we're concerned specifically about these: 550 5.7.64 TenantAttribution; Relay Access Denied Our analysis of the bounces suggests these are happening where we should be getting "User Unknown" ones, but these seem a bit ambiguous. I tried opening a ticket to Outlook Deliverability Support, but even after requesting an escalation, the team keeps pointing me to the Office365 support or this article: https://support.microsoft.com/en-us/help/3212877/-550-5.7.64-tenantattribution-relay-access-denied-smtp-error-when-sending-mail-through-exchange-online-protection The explanation provided in there seems unrelated as we're not sending through or to any Exchange/Office 365 servers. It seems, though, that both hotmail.co.uk and live.co.uk are now including protection.outlook.com in their MX entries. Thanks a lot in advance. regards, -- ____________________ *Daniel Baqueiro* Deliverability EMEA Groupon International Ltd. Connaught House |1 Burlington Rd | Dublin 4, Ireland
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