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An email sent by a server administered by me bounced back saying it failed the SPF check. Looking at the bounce message it had an IP different to that of the server sending the email. Then I found that the message which was bounced was actually sent to a relay server of the recipient since the receiving server was down at that time. when relaying the server to the final server it refused the email.

Is this a normal behavior?

If I'm configuring a postfix server which has a relay server in case of a service failure, is there a way to stop this kind of behavior.

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Edit: this isn't your fault, and there's not much you can do about it.

If, however, you're running a mail server that checks SPF records on inbound email, and you have servers that might receive email from the internet but pass it on to your main mail server instead of doing final delivery locally, then it's your job to make sure that you don't break SPF.

That means that your final mail server must exempt mail coming from the relay boxes from SPF validation, which will - as you have observed - fail. How you do this is implementation-dependent, but all good SPF implementations allow you to exempt certain sending IPs from validation, and on your main server you must so list all your relay servers.

You may also wish to do SPF checking on inbound email to the relay servers - I certainly would - but the main point is that your mail server must accept mail from the relay boxes without (SPF-related) question.

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  • thanks for the tip. The server which bounced the email is not a server run by me. I run the server which sent the mail. :) . And I think i should go out and learn a bit about spf implementation now.
    – eranga
    Oct 14, 2014 at 10:09
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    eranga, I did understand that, and I apologise for not making it clearer that I knew you were guiltless! The fault, in this case, is entirely with the receiving organisation - but I thought it best to approach the question from the "what are my obligations if I'm setting up the receiving servers" point of view.
    – MadHatter
    Oct 14, 2014 at 10:23

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