62281: Acronis Backup: backup of Office 365 mailboxes to a network share fails with "No more connections can be made to this remote computer at this time because there are already as many connections as the computer can accept"

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Symptoms

With a single backup plan, you are backing up several (more that 8) Office 365 mailboxes to a network share.

First 8 mailboxes are backed up successfully, then backup fails with:

Command has failed. TenantID=00000000-0000-0000-0000-000000000000
Windows error: (0x80070047) No more connections can be made to this remote computer at this time because there are already as many connections as the computer can accept

Cause

The maximum amount of parallel connections to the network share is set to 10 which is not enough for the backup plan: backup of Office 365 mailboxes is done in 8 parallel sessions and Acronis Agent process (mms.exe) uses the remaining 2 connections.

Solution

Increase amount of parallel connections that your share can handle.

For a network share on a Windows machine:

  1. Right-click the shared folder.
  2. Open the Sharing tab.
  3. Click Advanced Sharing.
  4. Set the required number in Limit the number of simultaneous users to.
  5. Click Apply and then click OK to save changes.

Alternatively, you can do this using Computer Management.

Windows 7 and Windows 8 / 8.1 allow a maximum of 20 users. Windows 10 allows a maximum of 15 users.

Windows Server 2008 /2008 R2 / 2012 / 2012 R2 / 2016 /2015 R2 allow a maximum is 16777216 users, which is practically unlimited, however, the actual allowed number of connections depends on the amount of obtained Client Access Licenses (CALs).

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