User A sends an email message with an attachment to User B. The attachment name has the following filename: Name.a.b.c.txt. When User B receives the attachment and opens it from Outlook he will see thatdots (“.”) from the file are replaced with blank spaces (instead of Name.a.b.c.txt the file will appear as Name a b c.txt).
How the attachment appears in Outlook in the received message:
How the filename appears when the attachment is opened in Outlook:
This behavior is not seen when saving first the attachment on your disk. If the attachment is first saved then the filename will contain the special characters.
Explanation for this behavior:
Outlook 2003 and 2007 have been designed keeping security as an important feature. The Security has been advanced on Outlook 2003, Outlook 2007 and Outlook 2002 Service Pack3. Attachments which contain the following special characters: ‘.’ ‘]’ ‘;’ ‘,’ ‘=’ embedded in the filename have potential security risks involved.
For this reason, the Outlook security will strip these characters out of filenames and replace them with a blank space.
We have seen cases when executables containing viruses were sent in this filename format (for example hello.exe.txt) as an attachment in Outlook. Double-clicking in Outlook on the file have the risk of executing directly the .exe file, so launching the virus:
Some examples below:
Win32.Netsky.P@mm : http://www.bitdefender.com/VIRUS-27915-en–Win32.Netsky.P@mm.html
If you want to have these special characters, I can suggest the following workarounds:
1) Do not use special characters in the filenames. You could use ‘_’ (underscore) or ‘-‘ (dash).
2) Save the attachment first before opening it in order to preserve the full name. The sender and recipient should use an antivirus to scan the files before opening it/sending it.