Backup email M365 problem

[kikanq]

Hi,

I am backing up Exchange M365 mailboxes for the first time.

I have created dynamic groups in EntraID for my tenant – I have 8 groups, each with about 100 users.
Each group is a separate backup task in my VBO365 console.

So I have 8 tasks to back up my employees' email boxes.
Each of these tasks will ultimately be handled by this proxy server: Windows Server 2022 (4CPU, 32GB RAM).
The proxy server has an iSCSI repository connected (the repository is a Synology NAS server).

For example, I run ONLY ONE TASK:
During the task, several mailboxes will perform their backup, but many of them have errors such as:

:: Processing archive mailbox test@myorganization.com failed with error:
An error occurred while sending the request.. An error occurred while sending the request..
Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host...
An existing connection was forcibly closed by the remote host.

or

:: Processing mailbox test@myorganization.com failed with error:
A connection attempt failed because the connected party did not properly respond after a period of time,
or established connection failed because connected host has failed to respond. (outlook.office365.com:443).
A connection attempt failed because the connected party did not properly respond after a period of time,
or established connection failed because connected host has failed to respond. (outlook.office365.com:443).
A connection attempt failed because the connected party did not properly respond after a period of time,
or established connection failed because connected host has failed to respond.

Please help me. What should I do in this situation? How can I fix this?

[aeph]

Let them run into a retry.

If this is the initial backup, it may happen that the first few runs return a corresponding message. These connection problems usually resolve themselves during the retries. Give the job time.

[karsten123]

disable exo throttling for initial backup

[kikanq]

disable exo throttling for initial backup

If you're talking about this: https://www.veeam.com/kb4198

I did it before running the first backup

[Mildur]

Hello Kikanq,

Please open a support case — the forum isn’t intended as an alternative to technical support as explained in red letters when creating a new topic.
Could you please share the support case ID for this issue? Without a case number, the topic will eventually be deleted by moderators.

Thank you for understanding,
Fabian

[Mike Resseler]

On top of what @Mildur has said... Guys on the forum here might be right because of your initial backup (which probable means a lot of data is needed and you are being throttled. (that error message basically means the API gateways are refusing you for that time).

But also check connectivity and see you are not getting into looks through proxy servers or firewalls.