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At my work we use Sendgrid to send automatic e-mails to the users of our platform. Since a couple of days the e-mails are going to spam on hotmail.com & outlook.com. This is weird because the DNS settings (DKIM & SPF) are correct & the e-mail headers also give me no sign why it should be marked as spam.

Even the spamfilter itself says it isn't spam

Below I've put several of the headers:

  • Authentication-Results
    • spf=pass (sender IP is 208.117.55.132) smtp.mailfrom=platformmail.secretview.nl; hotmail.com; dkim=pass (signature was verified) header.d=secretview.nl;hotmail.com; dmarc=bestguesspass action=none header.from=secretview.nl;
  • DKIM-Signature
    • v=1; a=rsa-sha1; c=relaxed/relaxed; d=secretview.nl; h=content-type:from:mime-version:to:subject; s=s1; bh=G9ItZEcyujTsrHF9IzImCn29pmw=; b=XUwb1SnsU65OlJRtQKQpuJqrkqEIw 9OfiHwo2lioUwy1YLSQqPGFx3c4STtvV4s6H2VOuE86wqWOLo34j1xo9QNjvFatl F5xELtRl13sqnWdScPMaU9EKqi/1zDxHlVxq1RpulfgVCjqhi6PWYGPkW354fgRq NShjYMcFSspwjA=
  • X-Forefront-Antispam-Report
    • EFV:NLI;SFV:NSPM;SFS:(98901004);DIR:INB;SFP:;SCL:1;SRVR:SN1NAM01HT089;H:o1.f.az.sendgrid.net;FPR:;SPF:None;LANG:;
  • X-Microsoft-Antispam
  • BCL:3;PCL:0;RULEID:(5000109)(4604075)(4605076)(610169)(650170)(651021)(8291501071);SRVR:SN1NAM01HT089;
  • X-MS-Exchange-Organization-PCL
    • 2
  • X-Exchange-Antispam-Report-Test
    • UriScan:(269995582827781)(86561027422486)(231433314529491)(194151415913766)(64217206974132);
  • X-Exchange-Antispam-Report-CFA-Test
    • BCL:3;PCL:0;RULEID:(444111536)(1540499029)(595095)(82015058);SRVR:SN1NAM01HT089;BCL:3;PCL:0;RULEID:(100000803101)(100110400095);SRVR:SN1NAM01HT089;
  • X-MS-Exchange-Organization-SCL
    • 1

If you want any other headers, just ask

Tom Droste
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    Microsoft products are weird. That's a fact. – LinuxBabe Dec 23 '17 at 05:15
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    Ask Sendgrid, as they need to maintain reputation for all customers and this could be affecting others. However, also consider your content, which can also trigger filters irrespective of configuration. – Simon Greenwood Dec 23 '17 at 09:41
  • I will ask Sendgrid. About the content: In the platform they apply for 'assignments' and those emails contain manditory information for the user. The content is specific for each assignment so it isn't duplicated what so ever. That being said, do you have specific tips? – Tom Droste Dec 23 '17 at 11:09
  • After knowing your problem and reading posts about email issues with Microsoft on the Internet, I will tell all my users not to use any Microsoft email address. Microsoft just can't get email right. – LinuxBabe Dec 23 '17 at 11:35
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    Possible duplicate of [How to send emails and avoid them being classified as spam?](https://serverfault.com/questions/48428/how-to-send-emails-and-avoid-them-being-classified-as-spam) – Jenny D Dec 29 '17 at 20:20
  • The reverse DNS of your IP might be an issue as well, although the comment/answer below about sendgrid and people marking it as spam may have some validity. – ivanivan Dec 30 '17 at 00:14

2 Answers2

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Sendgrid has clients that send a lot of advertising that is perceived as unsolicited by the final user. For every user that reports an email as spam the reputation of the sender goes down and all of the people using the service is affected. Reputation is usually attached to the ip classes that deliver the emails and to the domains. Domains of the relays, of the dkim signatures, of the envelope and header senders, of the links inside emails.

Rodolfo Saccani
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SPF and DKIM must not be seen as panacea for email deliverability problems. Period.

Depending on many factors (vendor, software & others...), they may increase chances for good outcome, or decrease chances of messages being bounced at SMTP handshake level, provide sender integrity or cause email servers to bounce spammers pretending to come from your domain name, and that's it. It is also important to know that there are senders with long-established good reputation that don't use this two techniques at all (although not using SPF is really weird in 2017).

I'd say your problem is well-known - Why Does hotmail still reject my emails? . With the details you have provided, I'd suspect that content of messages does have some significance to antispam software they are using - maybe try to alter content and see the results.

Miloš Đakonović
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