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+======Attachments have been removed or renamed======
+If you have received an email and one or more of its attachments have been removed or renamed, it might be a result of [[how_to:filtering_attachments|Attachment Filtering]].
+You can inspect the filtering rules by going to Administration Settings -> Settings -> Attachment Processing -> Filtering
+=====Double-extension=====
+One common scenario is where dates or other bits of information are included in the filename and separated by dots.
+This could potentially trigger the following rule:
+***.???.???**
+The rule detects a filename that ends in a dot, followed by three characters, followed by another dot, then three more characters. It is designed to prevent a common trick, where filenames are given a pretend extension, in front of the actual one.
+The trick is designed to make a recipient think a potentially malicious program is just a typical document. Anyone who is unfamiliar with the way filename extensions work in Windows may mistake that **file.doc.exe** is a Word document and run it.
+Unfortunately, this also means that some legitimate files may be filtered. For example: a file named **file2011.may.doc** would look suspicious and therefore be filtered, according to that rule.
+=====Workarounds=====
+If your attachments are being filtered, there are a few options:
+  - You might want to ensure **Change filtered attachment extension to make it unrunnable** is selected in the filtering settings
+    * This ensures the attachment is still accessible, but it would make it difficult for an inexperienced user to open the file.
+    * In the rare cases that such an attachment is legitimate, the user can be shown how to save the attachment, rename and open the file.
+    * The final character of the extension will be replaced with an underscore, so a Microsoft Word file named **file.123.do_** would usually need to be renamed to **file.123.doc**
+  - Ask the sender to adjust the way they format their filenames. For example; when writing dates, hyphens (-) and underscores (_) are usually suitable alternatives to dots.
+  - Redirect all emails with filtered attachments, to a particular user.
+    * In the filtering settings, select **Redirect messages with filtered attachment to**
+    * Redirect the messages to a user who has a good understanding of Windows filenames and the sort of files you would expect to receive.
+    * This user should then forward the messages, if appropriate, to the intended recipient.
+  - Remove or edit the rule that is filtering the attachment
+    * This is not recommended, because it exposes users to additional potentially unsafe files. Nonetheless, if filtering is affecting productivity, it may be the only suitable option.

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