Checking PST files for viruses before import in ExO

Question

Hello everyone,

unfortunately I did not find any information about this in the MS documents.

Situation:
With the PST import function the PST files are copied to an Azure-Blob storage and from there they are imported to the target mailbox by a PST import job.

Question:
Does one of the two processes (copy to Azure / import to mailbox) involve a virus check by Microsoft? Does Microsoft recognize contaminated PST files and how do they handle them? Are the files blocked (with which message) or is the data copied/imported without checking?

Does anyone here have information about this?

Answer 1

@David Jacobs

Based on my knowledge, Exchange Online doesn't provide additional immediate scanning for items when they are imported to the mailbox from Azure.

From the PST import workflow, we can know that M365 analyzes the data in the PST files before starting the import job, but it doesn't mention that M365 will provide virus scanning in this process. Since I mainly provide support for Exchange, if needed, you can post a new question specifically only with azure-blob-storage tag to know if Azure Blob provides any virus scanning feature.

For your reference: Overview of importing your organization's PST files.

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Answer 2

All messages will be scanned for malware. Now does that mean it will immediately catch PST imports in Azure? Don't know.
But if a message is infected. it will be caught in Exchange Online

https://learn.microsoft.com/en-us/microsoft-365/enterprise/microsoft-365-malware-and-ransomware-protection?view=o365-worldwide

Answer 3

HI @David Jacobs
Only when the messages are sent or received

https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/anti-malware-protection-faq-eop?view=o365-worldwide#does-the-service-scan-internal-messages-for-malware

For organizations with Exchange Online mailbox, the service scans for malware in all inbound and outbound messages, including messages sent between internal recipients.