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Symptom

Suddenly all emails older than a certain date have disappeared from my mailbox. But I didn't delete the emails.

Cause

Customers with this symptom suspect a technical problem with the server and are usually completely convinced that they have not made a mistake themselves. Bad conditions for getting to the bottom of the matter.

A mail server is not able to automatically delete individual mails according to certain criteria. One property of a server is that it only does what clients (i.e. e-mail programs) tell it to do with mail. For that reason it's a server, not a client. Everything that happens to e-mails on the server is initiated by a client, i.e. an e-mail program. The server exists to receive commands and to execute them. It doesn't give orders itself.

A technical error is ruled out because each email is saved in its own, individual file on the server's hard drive. Each of these files has its own file name and location on the hard drive. It is extremely unlikely that all files belonging to a mailbox are arranged in the same hard disk sector and that precisely those files with a certain time stamp would be destroyed in the event of a hard disk failure. All files are recorded in an index of the mailbox administration. If the files and the index do not match, the whole mailbox usually does not work. However, deleting a file does not change the index. If the mailbox is basically accessible, there is therefore no error between the index and files, i.e. the index must have been updated by a corresponding command from a client. This can only be done in the context of the delete instruction that a client has sent.

Real technical failures are very rare. If one hard drive was damaged in the event of such a failure, there is always another one that remains in operation and can supply the same data. In the very unlikely event of a total failure, hard disks or controllers would be so badly damaged that all data in the system would have to be laboriously restored from a data backup. Selective damage to files with a specific time stamp is practically impossible. In order to delete files "older than ...", an explicit instruction would be required, which specifically refers to the subfolder in which the relevant mailbox files are stored. Selective deletion of such files would also result in index errors on the mail server and would manifest itself in such a way that the mailbox would no longer function at all until the index is repaired.

What is the real cause?

In truth, e-mails are missing from a mailbox when a client, i.e. an e-mail program, has deleted these e-mails. This can happen accidentally by moving folders or emails by a user, but it can also happen automatically through client settings (e.g. auto-archiving or automatic deletion after retrieval from the mailbox).

Solution

If several clients access the same mailbox, it is sufficient to misconfigure one client so that all clients can no longer see the mail. It may be that you haven't deleted or moved any emails yourself, but maybe an employee did it?

• Check whether the e-mails were accidentally deleted and whether there is still a copy in the recycle bin of the mailbox.
• Check whether you or an employee has moved mails to another folder. Very often users accidentally move e-mails to other folders and then cannot find them again.
• Check that all mail programs are using the correct root folder path for the mailbox. The root folder path must be configured the same everywhere. Differences between different clients can lead to the fact that some clients lose access to mails because they have been moved to a path that cannot be reached from their root folder path. For more information on the root folder path, see the related FAQ articles.
• Check whether you or an employee who also has access to the mailbox has archived the content. In some mail programs this can be done very quickly and easily with a single click of the mouse. In Microsoft Outlook you can, for example, archive mails with a default setting by a click on an icon:

  

  mails are deleted from your mailbox by the mail program, but the mails are still in the archive file.
• Check whether you have activated automatic archiving in one of your mail programs. Automatic archiving usually saves older mails (e.g. "all mails older than 14 days") in an archive file and deletes it from your mailbox to free up space in the mailbox. In Microsoft Outlook, for example, you can set up automatic archiving of old mails with "File"> "Options"> "Advanced"> "Settings for auto-archiving":

  

• Check whether in one of your mail programs you have set that mail that has been retrieved from a mailbox should be deleted after a certain period of time. This setting is available in almost every common mail program, e.g. in Microsoft Outlook

  

  in Mozilla Thunderbird

  

  also in most other mail programs and smartphone mail apps.

Overview of frequently asked questions