question about *web/email

[Alain Stucki]

Hello
We are sending PDF invoices to our customers with *web/email. The mail server is the one provided by a hosting company. Works great except one customer doesn't receive them. I get an email from their Exchange server saying that there is a problem with DMARC and that's why the email is rejected. However, when I send an email to that customer by using desktop Outlook (classic) with the same username, passwort and SMTP-settings, the email arrives at the customers inbox. Also, if I send emails with *web/email to GMAIL addresses or any other customers, they all go through fine and I never get a message about DMARC problems. If I send it to my test account and have a look at the email headers, there I see DMARC=pass, DKIM=pass, SFP=pass.

I have also tried different mail servers for sending (smtp) but no matter which smtp server I use, when I send an email with *web/email to that customer I get to see that error-mail about DMARC.

So first I thought it's a problem on the customers side as I have only had problems with 1 customer so far. But it doesn't make sense to me that the problem only occurs when I send him an email with *web/email but not with outlook.

So my question is: Is it possible that *web/email on my version (2016) has some problems with DMARC in combination with Exchange-servers?

[yonman]

Hi Alain, 
 
You mention in your note that 'the mail server is the one provided by a hosting company'.  That leaves a lot of questions, Alain. 

But, the fact that only one customer is not receiving your email suggests the problem lay with the recipient's Exchange server itself.  Is there an admin who manages that Exchange server?  They should be able to see in their error logs a need to whitelist your domain or add your domain or sender name to an allow-list.

Emails going to this same recipient through Gmail or Outlook are flagged as safe because they are going through authorized email servers, over a secure port, with full encryption.  Something about your email 'hosting company' is being flagged as suspicious.

Very best,
Yonman

[Mike King]

There are a number of reasons for your DMARC to be rejected and its possible that the client having trouble might just be more fussy.

Here is an article that highlights a number of potential DMARC issues that could be causing the problem you are having.

https://dmarc.org/2016/07/common-problems-with-dmarc-records/

Also if your application is adding custom headers to the email make sure they are correct and don't have things like an accidental trailing semi-colon on a header.  That may cause a header your email server might add to render incorrectly.

[Alain Stucki]

Thank you both for your help!

As my application is not adding anything to the header (just using  *web/email) and as it's really just one customer whose exchange server is rejecting our emails, I'm more and more convinced it must be a problem on his side, not ours. And I found out that the email address where we send the mails to is not an exchange server but a mail account hostet by his provider and there it's forward it to a Microsoft exchange address (like bla.bla.bla@companyname.onmicrosoft.com). And it's that exchange server that rejects the mails. So I guess hat when the emails are forwarded to the onmicrosoft.com domain, something happens to the email that makes the microsoft server reject them.

That would explain a lot. Except that when I send the emails using Outlook (classic) instead of our application using *web/email, then the mails aren't rejected. Maybe this is because Outlook creates the headers differently than *web/email. Anyway it's just like my father said: we use computers to solve problems we wouldn't have without them