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We're building a service that sends emails for Office365 users using EWS (or REST API) with OAuth2. For some reason when testing email sending using our _.onmicrosoft.com accounts we get the following errors:

Your message wasn't delivered because the recipient's email provider rejected it. Remote Server returned '550 5.7.501 Access denied, spam abuse detected.

Noticed that DKIM signature is missing when emails are sent via EWS/API.

Authentication-Results: target-domain; dkim=none (message not signed)
header.d=none;target-domain; dmarc=none action=none
header.from=sender-domain.onmicrosoft.com;
Received: from DM3PR1201MB1039.namprd12.prod.outlook.com (10.164.197.149) by DM3PR1201MB1039.namprd12.prod.outlook.com (10.164.197.149) with Microsoft SMTP Server (TLS) id 15.1.534.14; Wed, 6 Jul 2016 16:42:03 +0000
Received: from DM3PR1201MB1039.namprd12.prod.outlook.com ([10.164.197.149]) by DM3PR1201MB1039.namprd12.prod.outlook.com ([10.164.197.149]) with mapi id 15.01.0534.020; Wed, 6 Jul 2016 16:42:03 +0000

Emails are delivered just fine if we send them manually from our Office365 UI.

Any idea why this may be happening?

Alexey
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  • Can you send the message successfully if you send the message manually without DKIM? – Fei Xue Jul 21 '16 at 01:27
  • Just tried disabling DKIM in my O365 account and sent an email from Outlook. Emails are delivered fine with or without DKIM enabled when sending from Outlook or web based O365. – Alexey Jul 21 '16 at 17:09
  • Today actually our EWS/API tests are delivered. Authentication-Results: mx.google.com; dkim=pass header.i=@ours.onmicrosoft.com; spf=pass (google.com: domain of skilbert@ours.onmicrosoft.com designates 104.47.42.127 as permitted sender) Something got fixed or it is dependent on X-Originating-Ip which is changes in our case. – Alexey Jul 21 '16 at 17:11
  • Happened today again: Authentication-Results: ; dkim=none (message not signed) header.d=none;; dmarc=none action=none header.from=ourdomain.onmicrosoft.com; – Alexey Jul 22 '16 at 22:00
  • One difference is Authentication-Results: mx.google.com; vs Authentication-Results: ; although in both cases we sent to which is hosted in Google Apps – Alexey Jul 22 '16 at 22:01
  • Add-ons, i.e. Boomerang, can't send emails either. – Alexey Jul 27 '16 at 00:31

0 Answers0