An existing connection was forcibly closed by the remote host

[NorthGuard]

I just implemented Backup for M365, configuring the jobs as follows:

Mailbox job
- roughly 71 mailboxes
- selecting from a dynamic entra group where usertype = Member and only selecting Mail, Archive, Group Mail

Sharepoint-OneDrive job
- manually selected all Sites for Objects to Backup Up

Teams job
- manually select all Teams sites/channels

I was reviewing the results this morning and am seeing a bunch of mailboxes failing with the following error:
Processing mailbox <user> failed with error: 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. :: 0:44:35

The Teams job is also failing with a different error:
9/5/2024 3:21:05 PM :: Failed to process team: <teamName>. Failed to process team files: <teamName> The SSL connection could not be established, see inner exception.. The remote certificate is invalid according to the validation procedure: RemoteCertificateNameMismatch, RemoteCertificateChainErrors :: 4:51:33

I was doing some preliminary research and am not yet seeing a clear fix for either of those issues.

Any suggestions would be appreciated!

[Polina]

Hi NorthGuard,

It could be a firewall or something else that is preventing the Veeam service from connecting.
The best would be to open a support case, provide our engineers with your logs, and let them check your network and settings.

Thanks!

[NorthGuard]

I don't think it is a firewall issue as it does backup quite a few mailboxes... just fails on others