Reverse DNS Lookup

stavros mitchell 56 Reputation points
2020-11-30T20:52:16.013+00:00

Hey Everyone we have a new client that asked us to looking into setting up reverse DNS lookup because they run a spoofing test. To my knowledge this is not possible am i correct?

The client already has ATP set up with microsoft standard baseline policy

thanks for the help

YOU SHOULD NOT RECEIVE THIS EMAIL!

This email system failed to validate the source domain (reverse DNS lookup) This security issue is used often to compromise users from lookalike domains, your inbound servers do not check if the domain is valid before accepting the email. This security issue is used often to compromise users, steal data, and manipulate internal affairs.

To correct; Configure your inbound email servers reverse DNS correctly and try again. Go to emailSpoofTest.com for details, reference Email 5

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Exchange Server Management
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  1. Andy David - MVP 141.5K Reputation points MVP
    2020-11-30T21:09:47.64+00:00

    You need to setup a SPF record for the sending domain. Does it exist?
    If using office 365 to send email, then add their info to the clients SPF record:

    https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/set-up-spf-in-office-365-to-help-prevent-spoofing?view=o365-worldwide

    include:spf.protection.outlook.com

    The reverse IPs for Office 365 ( PTR ) already exist for these, so you dont need to add for the clients domain.

    You can check here:

    https://mxtoolbox.com/

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  2. KyleXu-MSFT 26,206 Reputation points
    2020-12-01T02:31:40.537+00:00

    @stavros mitchell
    What version of your mail server?

    This email system failed to validate the source domain (reverse DNS lookup) This security issue is used often to compromise users from lookalike domains, your inbound servers do not check if the domain is valid before accepting the email. This security issue is used often to compromise users, steal data, and manipulate internal affairs.

    If you cannot send email from your mail server to target mail server. You can try to contact you ISP to add a reverse DNS lookup for your mail server. By the way, if your mail server doesn't have SPF record, try to add it together. Lack of SPF records will be rejected by many mail servers.


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