The mail server tells me that it has deleted an image file that could be a virus file - Why?
It is possible that an incoming email contains a message from the mail server’s anti-virus system that an attached file has been deleted because it was a potential virus carrier. This will normally only happen for files of these types:
.scr
.pif
.vbs
.shs
.exe
.com
.bat
.hta
Therefore it may seem strange that a simple JPG picture file would be deleted by the system - especially since JPG in it self is a very commonly used file standard.
The explanation lies in the name of the file: If the filename contains special language characters (like 'æøåüöäé') some mail programs will change the name of the file, like the example below:
Værdiskab_01.jpg
to
Værdiskab_01.jpg-=?ISO-8859-1?Q?V=E6rdiskab=5F01.jpg?=
The anti virus system will therefore see the file type as
.jpg?=
- And since this isn't a valid file type, it will see this as an attempt to sneak a virus file past the system, and it therefore reacts by deleting the file. The solution could be to change the name of the file to something not containing special characters:
Vaerdiskab_01.jpg
NOTICE: Since it isn't all mail programs that have this behaviour some users might not see this problem at all, and have no problem sending attached files with international characters.