Constant sync error pop-up messages from client for files in use.

The Basics

  • Nextcloud Server version (e.g., 29.x.x):
    [Nextcloud Hub 10 (31.0.7)

  • Operating system and version (e.g., Ubuntu 24.04):
    client: Windows 10 22H2

  • Web server and version (e.g, Apache 2.4.25):
    n/a

  • Reverse proxy and version _(e.g. nginx 1.27.2)
    n/a

  • PHP version (e.g, 8.3):
    n/a

  • Is this the first time you’ve seen this error? (Yes / No):
    Yes

  • When did this problem seem to first start?
    when started syncing the file in question

  • Installation method (e.g. AlO, NCP, Bare Metal/Archive, etc.)
    n/a

  • Are you using CloudfIare, mod_security, or similar? (Yes / No)
    No

Summary of the issue you are facing:

I’ve checked the existing thread, but it is now closed, and no solution was offered.

Trying to sync mail store (.pst file) and getting a constant error pop-up every few seconds if the file is in use (Outlook is opened).

I understand what is happening, and I close Outlook to allow for a sync, but the constant pop-up is unbearable.

I’m on Windows 10, and I was expecting Nextcloud to use VSS and delta transfer. Is this not the case?

Pausing sync for all or disabling notifications, or ignoring this file is out of the question for obvious reasons. Any other suggestions?

Steps to replicate it (hint: details matter!):

  1. Have a mail program with a mail store file.
  2. Try to keep that file synced and use the mail program at the same time.

Log entries

#=#=#=#=# Propagation starts 2025-09-07T17:19:54Z (last step: 14401 msec, total: 14401 msec)
||poczta.pst|64|1|1757265317|47a49f476dc2aa8ebbc4c6a88ff6fdb8|5155750912|00037380ococm5jgj3ml|1|An unexpected error occurred. Please try syncing again or contact contact your server administrator if the issue continues.|0|5155750912|1757262459|7318a569-3aae-48d9-9275-c7a539fe5786|
#=#=#=# Syncrun finished 2025-09-07T17:19:55Z (last step: 1007 msec, total: 15409 msec)
#=#=#=# Syncrun started 2025-09-07T17:21:46Z
#=#=#=#=# Propagation starts 2025-09-07T17:21:59Z (last step: 12622 msec, total: 12622 msec)
17:24:32||poczta.pst|64|1|1757265711|531f36a1b22a3f41a6c8ba31066dfe57|5155750912|00037380ococm5jgj3ml|13||204|5155750912|1757262459|1ce347dd-45a0-4908-bccc-1788429af6b8|
#=#=#=# Syncrun finished 2025-09-07T17:31:44Z (last step: 584990 msec, total: 597612 msec)
#=#=#=# Syncrun started 2025-09-07T17:32:22Z
#=#=#=#=# Propagation starts 2025-09-07T17:32:22Z (last step: 315 msec, total: 315 msec)
||poczta.pst|64|1|1757266315|531f36a1b22a3f41a6c8ba31066dfe57|5155750912|00037380ococm5jgj3ml|1|An unexpected error occurred. Please try syncing again or contact contact your server administrator if the issue continues.|0|5155750912|1757265711|0716f206-999a-4ecd-89d7-ce07208e6cd9|
#=#=#=# Syncrun finished 2025-09-07T17:32:23Z (last step: 996 msec, total: 1311 msec)
#### Nextcloud
Please provide the log entries from your Nextcloud log that are generated during the time of problem (via the *Copy raw* option from *Administration settings->Logging* screen or from your `nextcloud.log` located in your data directory). Feel free to use a pastebin/gist service if necessary.

Configuration

Nextcloud

[General]
clientVersion=3.17.1 (build 20250818)
confirmExternalStorage=false
crashReporter=true
isVfsEnabled=false
launchOnSystemStartup=true
monoIcons=false
moveToTrash=false
newBigFolderSizeLimit=500
notifyExistingFoldersOverLimit=false
optionalServerNotifications=true
overrideLocalDir=
overrideServerUrl=
promptDeleteAllFiles=false
showCallNotifications=true
showChatNotifications=true
showInExplorerNavigationPane=true
stopSyncingExistingFoldersOverLimit=false
useNewBigFolderSizeLimit=false

[Accounts]
0\Folders\1\localPath=C:/Users/***/Nextcloud/
0\version=13
version=13
0\Folders\1\journalPath=.sync_51633e072a74.db
0\url=https://***.***.cloud
0\Folders\1\targetPath=/
0\dav_user=***
0\Folders\1\paused=false
0\displayName=***
0\Folders\1\ignoreHiddenFiles=false
0\serverVersion=31.0.7.1
0\Folders\1\virtualFilesMode=off
0\serverColor=@Variant(\0\0\0\x43\x1\xff\xff\0\0gg\x9e\x9e\0\0)
0\Folders\1\version=2
0\serverTextColor=@Variant(\0\0\0\x43\x1\xff\xff\xff\xff\xff\xff\xff\xff\0\0)
0\Folders\1\navigationPaneClsid=@Variant(\0\0\0\x7f\0\0\0\x6QUuid\0\x17\x92\xa1\xd7\r*CU\xa2\x97\xe0\xc7h\xa6\x11\xd2)
0\serverHasValidSubscription=false
0\encryptionCertificateSha256Fingerprint=@ByteArray()
0\networkProxySetting=1
0\networkProxyType=2
0\networkProxyHostName=
0\networkProxyPort=8080
0\networkProxyNeedsAuth=false
0\networkProxyUser=
0\networkUploadLimitSetting=1
0\networkDownloadLimitSetting=1
0\networkUploadLimit=90000
0\networkDownloadLimit=90000
0\webflow_user=***
0\authType=webflow
0\FoldersWithPlaceholders\2\localPath=C:/dane/
0\FoldersWithPlaceholders\2\journalPath=.sync_74d17699eea0.db
0\FoldersWithPlaceholders\2\targetPath=/Dane
0\FoldersWithPlaceholders\2\paused=false
0\FoldersWithPlaceholders\2\ignoreHiddenFiles=false
0\FoldersWithPlaceholders\2\virtualFilesMode=wincfapi
0\FoldersWithPlaceholders\2\version=3
0\FoldersWithPlaceholders\2\navigationPaneClsid=@Variant(\0\0\0\x7f\0\0\0\x6QUuid\0\xe6:\x96\x8e\xbeKF\xae\xb8\x1b\xdc\xd1\xe7\xc7\xa7O)

[Settings]
geometry=@ByteArray(\x1\xd9\xd0\xcb\0\x3\0\0\0\0\x2\xf4\0\0\0\xcf\0\0\x4\xf7\0\0\x3W\0\0\x2\xf4\0\0\0\xed\0\0\x4\xf7\0\0\x3W\0\0\0\0\0\0\0\0\b\0\0\0\x2\xf4\0\0\0\xed\0\0\x4\xf7\0\0\x3W)

Hey @Pikor welcome to the Nextcloud community :waving_hand:

I’m certainly not an M$ type of person and I don’t use Outlook and know nothing about the workings of mailstore, but what you’re trying to do is synchronise an active database (file)… even if you stop your mail client and mailstore, its safe to presume that database (file) is active and will prevent sync.

so unless you stop the service, so that the database (file) is completely inactive you will not be able to sync that .pst file without errors.

@scubamuc
I resolved this by creating a task which checks for the modification stamp and, if the file was not modified for more than 5 minutes, copies it to the Nextcloud folder.