Need to delete .OST files

WalterH

I have a problem with two customers where we regularly have to delete some .OST files because Outlook in caching mode, no longer retrieves new emails from the server. However, only two or three mailboxes are affected; the other approximately 80 or 200 mailboxes do not have this problem. One customer was migrated from Kopano, all Kopano tools such as KOE and Zarafa Client were deleted from the PCs, and all other remnants such as orphaned Kopano files were also removed from the PCs. The second customer was migrated from Exchange.
Grommunio is the current supported edition.

Question: Does anyone else have this problem with mailboxes, where Outlook no longer retrieves new emails from the server, and is there a solution for it?

I am grateful for any tips.

ozy

Got the same on one mailbox opened by three computers where only one encounters the problem.

The one that has problems uses o365 whereas the one ones use office 2021.

Server has no migration history.
I have no idea what happens, but I can outrule the mailbox itself because of the above explanation.

Andy

Some times at my installation also, usually after updates.

WalterH

It has nothing to do with updates for my customers; there have been no updates for the Supported Edition for about six weeks (except for two minor updates, each with one commit, which have not yet been installed). It must be something else.

ozy

Got another mailbox that doesn't sync the inbox anymore today.
This time, the outlook client was Office 2021 Pro Plus, so nothing to do with O365.

Interestingly, there are lot of sync errors like this one since sync stopped working (sorry for the french logs):

17:15:02 Synchronisateur Version 16.0.19127
17:15:02 Synchronisation de la boîte à lettres 'MAILBOX NAME' en cours
17:15:02 Synchronisation des modifications locales dans le dossier « Boîte de réception » en cours
17:15:02 Erreur lors de la synchronisation du dossier
17:15:02 		 [80040102-501-80040102-430]
17:15:02 		 Echec de l'opération du client.
17:15:02 		 Banque d'informations de Microsoft Exchange
17:15:02 		 Pour plus d'informations sur ce problème, cliquez sur l'URL ci-dessous :
17:15:02 		 https://www.microsoft.com/support/prodredirect/outlook2000_us.asp?err=80040102-501-80040102-430
17:15:02 Terminé

Btw, I didn't touch the grommunio server or even reboot it (runs gromox-2.48.145.gc40fe13).
There's no need to delete the whole OST file, one can just "delete offline content" than "update this folder" in order to fix the problem, until it happens again.

It looks indeed like something random (perhaps a bad formatted mail ?) makes the offline cache and the server splitbrain at some point.

Andrew

I've experienced a similar issue a few times. I can't explain all of the instances, but one case that I've found that can definitely cause it is if something between Grommunio and Outlook alters the traffic. In my case there is a Web Application Firewall in front of the Grommunio server and occasion I've seen it block Outlook traffic because of a false positive detection. The WAF sends a 403 response page when this happens, but for some reason Outlook must try to parse the HTML in the response as MAPI/HTTP and corrupts its cache in the process.

ozy

Andrew In my case, that's not a valid explanation, since 3 users share the same mailbox behind the same firewall, and only one user is concerned.