Mailboxes get slow and inaccessible. No new messages show, but they are delivered

[in4]

Hello everybody,
we've been dealing with the following problem for some time now.
Single mailboxes become very slow and sometimes inaccessible, with new messages not showing in desktop clients or webmail interface. The message tracking logs indicate that incoming messages are received and delivered to the affected mailbox.
The Windows event viewer shows this error repeatedly:

Code: Select all

General: (MailEnable IMAP Service (C:\PROGRA~2\MAILEN~1\Bin64\MEIMAPS.exe) error: 0) [MEIMAPS.exe] Failed to serialise index: M:\Mail\[domainName]\MAILROOT\[mailboxName]\INBOX. A File Access error occurred when opening the file (was retried for 40 seconds). No data can be written.

The rate at which this is happening is quite slow (1 mailbox is affected every 3 days or so).
The affected mailboxes become slower and slower, stop showing new received messages and become unusable. They do not recover.
Other threads in this forum suggested looking for permissions to the folder, which I checked, and recommend upgrading MailEnable to the latest version. Is this a good advice? Are there risks in upgrading MailEnable?
Thank you.

[MailEnable-Ian]

Hi,

What version of MailEnable are you running? You need to ensure your running the latest version as there has been fixes core services in particular the IMAP service that you need to apply. The upgrade requires minimal downtime and will retain your existing configuration and data.