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[Migrated from MSDN Exchange Dev]internet ISP is added

Lucas Liu-MSFT 6,166 Reputation points
2020-10-29T08:07:32.177+00:00

[Note] This thread was originally posted on MSDN. As the MSDN Exchange Dev forum mainly focuses on developing issues and the TechNet Exchange forums for general questions have been locked down, we manually migrated this one to Microsoft Q&A platform to continue the troubleshooting.

we have two internet provider (Main link and backup link) when we switched for the second ISP internet provide we does not receive external email and i am listing down the dedicated environment

Exchange 2016

Mail Gateway

Public DNS

therefore should we update the real IP for the second ISP somewhere to solve this problem , pls advise

Edward

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Lucas Liu-MSFT 6,166 Reputation points
    2020-10-29T08:09:12.797+00:00

    Hi Edward,
    Did the problem occur after you changed your ISP?
    Did the external sender receive an NDR after sending it failed?
    First, please contact your ISP and check whether your DNS records are set correctly, including MX records and A records.Please make sure to point to the correct Exchange server.
    Check your firewall settings, whether the necessary ports are opened, and SMTP communication can pass smoothly.

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