Delivery has failed

Glenn Maxwell 9,771 Reputation points
2022-07-06T11:14:23+00:00

Hi All

I am using exchange 2016 hybrid environment. One of my user is sending email to external domain user and he is getting the below NDR. As per external domain user Message is being rejected by SPF policy. How can i check at my end if it is related to SPF.

Delivery has failed to these recipients or groups:
user@extdomain.com
A communication failure occurred during the delivery of this message. Please try to resend the
message later. If the problem continues, contact your email admin.

Diagnostic information for administrators:
Generating server: myemailgateway.com
user@extdomain.com
mail.extdomain.com
Remote Server returned '554 5.5.0 <mail.extdomain.com #5.5.0>'

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Accepted answer
  1. Joyce Shen - MSFT 16,631 Reputation points
    2022-07-07T03:14:03.277+00:00

    Hi @Glenn Maxwell ,

    The sender may receive the following non-delivery report (NDR) that contains the 5.5.0 error code. This code indicates a generic SMTP failure.

    Typically, this problem occurs if the destination SMTP server performs a reverse lookup and if one of the following conditions is true:

    The IP address does not match the domain name that is used in the return address of the e-mail message.
    A pointer (PTR) record does not exist or is not valid for the source SMTP server's IP address.
    https://mxtoolbox.com/ReverseLookup.aspx

    You may also take a look at the discussion here: smtp error 5.5.0 544
    That is an error being generated by your ISP. It isn't an Exchange error. You will need to contact them to establish whether they can support additional domains through their smart host.


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  1. Andy David - MVP 138.6K Reputation points MVP
    2022-07-06T13:43:53.25+00:00

    What indicator do you have its a SPF issue?

    That NDR can also mean the recipient rejected it as SPAM.

    You can check your SPF record to ensure its valid:

    https://mxtoolbox.com/spf.aspx

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