Author Topic: Avast Anti-Virus Business breaks Exchange Autodiscover  (Read 292 times)

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Offline tetranet

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Avast Anti-Virus Business breaks Exchange Autodiscover
« on: May 14, 2024, 09:45:27 AM »

A customer operates an Exchange 2019 on-premise, which receives its emails from a provider's mail server using a POP connector.
On client computers running Avast Business, when setting up an Outlook profile and starting Outlook with an existing profile, the Exchange server in the local network is not recognized, but according to the pop-up window, the autodiscover address of the email provider on the Internet is used to determine the mailbox. Since no Exchange mailbox exists at the provider, logically no mailbox is found.
If an nslookup is performed on the autodiscover address in the LAN on a client with Avast, no IP address is returned by the internal DNS.
However, all these problems disappear if Avast is completely deactivated on the affected clients. If the Avast protection modules are reactivated, the problems described reappear.
So a setting in Avast is interfering with autodiscover and/or name resolution. I already disabled Real-Site in the appropriate rules in the Avast Management Console, but to no avail.

Can someone tell me which setting it could be or which function controls the behavior regarding name resolution (because I think this is the cause of the problem) in Avast.