MailEssentials may sometimes quarantine legitimate email messages that have Microsoft Office attachments (*.docx, *.xlsx, *.pptx) and report such email messages as having corrupt archives.
This article describes the cause and provides a solution to address this problem for cases where emails containing Microsoft Office attachments are quarantined and wrongly flagged as having corrupt archives in the attachments. The article also provides a workaround when the quarantined emails are as a result of actual corrupt attachments.
Emails containing Microsoft Office attachments will be blocked and moved to the quarantine if there is a third party anti-virus or backup software running on the MailEssentials server and scanning the GFI directories.
Anti-virus and backup software are known to cause MailEssentials to malfunction due to Operating System-level file contention and locks which prevent the email security filters from scanning the same files simultaneously. As a result, the decompression engine will report the inaccessible files as corrupt archives and move the associated emails to the quarantine.
The quarantined emails will be flagged as containing corrupt archives on the dashboard logs as well as on the quarantine web page as shown below.
When this happens, the email recipients will complain of not receiving emails containing Microsoft Office document attachments.
MailEssentials can block and quarantines legitimate emails that have Microsoft Office (*.docx, *.xlsx, *.pptx) attachments as having corrupt archives due to the following reasons:
- The attachments have unreleased Operating System file locks caused by Anti-virus or backup software
- The attachments are contained in a corrupt archive
The first troubleshooting step should be to rule out file locking interference from third party Anti-virus and backup software by excluding the MailEssentials directories from being scanned by all Anti-Virus and Backup software, including Windows Defender that is part of the Windows Operating System.
This linked article on Recommended Antivirus and Backup Exclusions provides details on which directories must be excluded for different installation environments in order to ensure MailEssentials scanning proceeds uninterrupted.
However, if the problem persists despite configuring the exclusions described above, the likely reason is that the files are in fact contained in a corrupt archive therefore the workaround to ensure email delivery would be to exclude scanning of *.docx, *.xlsx, *.pptx and any other file types being detected as corrupt archives by the Decompression Engine.
Follow the below steps to achieve this:
- Open the MailEssentials Configuration console and expand Content Filtering.
- Navigate to the Decompression Engine node.
- Click on the Scan within archives rule;
- Select Enable exclusion and add the respective file types being quarantined;
- Click Apply.
- Select Check corrupted archives and click Disable Selected.
For the already quarantined items, check, and, release or delete as necessary as described in Managing Quarantined Emails.
Once the recommended exclusions have been configured on the Anti-Virus and/or Backup software, confirm that emails are now being delivered by sending a test email containing a Microsoft Office attachment.