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Exchange online forwarding

Alain Sorrentini 26 Reputation points
2020-08-17T09:45:03.163+00:00

Hi all,
I have a problem with email forwarding and I hope for your help.

Example:
myFirstAccount@example1.com --> is the mail mailbox that forwards the email to mySecondAccount@example2.com
mySecondAccount@example2.com --> is the mailbox that receives the email forwarded from the first mailbox
customer@example3.com --> is my customer's mailbox

If customer@example3.com sends an email to myFirstAccount@example1.com and mySecondAccount@example2.com is temporarily out of order, my customer receives a message from microsoftexchange@mydomain.onmicrosoft.com with the error "Delivery failed for the following recipients or groups: mySecondAccount@example2.com".

I don't want my customer to know that I'm forwarding my email to my second account.

Is possible to avoid this behavior?

Thank you for your help.
AS

Microsoft Exchange Online Management
Microsoft Exchange Online Management
Microsoft Exchange Online: A Microsoft email and calendaring hosted service.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Andy David - MVP 142.7K Reputation points MVP
    2020-08-17T12:33:38.42+00:00

    Hi @Alain Sorrentini
    Ok, thats a different the issue. You are forwarding and that breaks all the SPF/DMARC checks.

    Office 365 has a mechanism to address this:
    https://learn.microsoft.com/en-us/office365/troubleshoot/antispam/sender-rewriting-scheme

    But, this is really on the other provider. If they are dropping this, you need to talk to them to see if you can whitelist these messages

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  1. Alain Sorrentini 26 Reputation points
    2020-08-17T12:38:03.1+00:00

    Thanks for your explanation and your time.

    1 person found this answer helpful.
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  2. Andy David - MVP 142.7K Reputation points MVP
    2020-08-17T11:14:35.76+00:00

    There is no way to prevent NDRs per mailbox in that way. If there is a problem with any mailbox in your tenant. Exchange Online is going to report it to the sender.
    Why is the forwarding to mailbox "out of order"?

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  3. Jon Alfred Smith 541 Reputation points
    2020-08-17T12:02:40.85+00:00

    In stead of forwarding, you could try with a mail flow rule (transport rule). You do that in Exchange Online.

    The logic would be:
    If a message is sent to myFirstAccount do the following
    Add following recipients in the To-Address: mySecondAccount

    In order to test if a NDR is generated, you would temporally need to invalidate the To-Address. Easiest way would be to add a second SMTP address to mySecondAccount.

    First you test if the rule works, then you remove the secondary SMTP address and check if a NDR is generated to the original sender.

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  4. Alain Sorrentini 26 Reputation points
    2020-08-17T12:13:23.017+00:00

    Thank you for your reply.

    The message sent to my customer says:
    mySecondAccount@example2.com
    mxbw.lb.bluewin.ch
    Remote Server returned '554 5.2.0 <mxbw.lb.bluewin.ch #5.2.0 smtp;554 5.2.0 sc971: SPF hard fail>'

    Note: mySecondAccount@example2.com is managed by another provider (not Microsoft).

    Thanks again
    AS

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