Maximum concurrent connections of o365 mailbox?

Question

I would like to know the Maximum concurrent connections of o365 mailbox,
As the user reported that they cannot view the mailbox when we have backing up the mailbox from Veeam.

Answer 1

@Mark Chiang

This article talks about this limitation about Exchange online mailbox, however it doesn't contains the limitation about mailbox connection. So, I would suggest you open a service request to confirm with Office 365 team. They may could find some information for you.

Based on your description, I think there exist limitation about Exchange online mailbox connection, why not set up a scheduled task for backup at night? (Personally, Microsoft will ensure the continuous operation of Office 365, and there is no need for backup)

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Answer 2

Hi @Mark Chiang ,

They're discussing this over here, perhaps it could be helpful information:
https://serverfault.com/questions/672493/is-there-a-documented-maximum-number-of-users-you-can-have-connected-to-an-offic

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Best regards,
Leon