We have an in-house Exchange 2007 server (on SBS2008) and to our surprise, as of yesterday, Comcast decommissioned almost all their SMTP/Mail servers and migrated to MS Office365. So they gave us an "onmicrosoft.com" username, password and new SMTP settings. When I enter them in the smarthost config I get a bounce-back almost immediately. I've been searching for approx 24hrs straight and can't seem to find any solution. Below is the NDR. BTW, already tried the uncheck, "require all senders are authenticated" in Distribution Group "all users" and still the same error of not having permissions. The first part of the NDR makes me think it's an Exchange issue, then it goes onto saying that the Office365 server rejected the email. I've been on the phone with Office365 support and they're not sure what the story is.
Any help would be awesome.
Thanks so much.
Delivery has failed to these recipients or distribution lists:
Your message wasn't delivered because of security policies. Microsoft Exchange will not try to redeliver this message for you. Please provide the following diagnostic text to your system administrator.
The following organization rejected your message: BN6PR20CA0072.outlook.office365.com.
Diagnostic information for administrators:
Generating server: SERVER.ERB.local
CO1PR15CA0067.outlook.office365.com #550 5.7.60 SMTP; Client does not have permissions to send as this sender [SN6PR1901MB2143.namprd19.prod.outlook.com] ##
Original message headers:
Received: from SERVER.ERB.local ([fe80::3d0c:2ce5:3688:1188]) by
SERVER.ERB.local ([fe80::3d0c:2ce5:3688:1188%10]) with mapi; Wed, 20 Dec
2017 18:57:21 -0500
From: Mike Smith <email@example.com>
To: "firstname.lastname@example.org" <email@example.com>
Date: Wed, 20 Dec 2017 18:57:20 -0500