The following attachment extensions are blocked by the server to protect you from viruses. If you need to send such files, simply add them to a zip file and attach the zip file.

ad[ep]
ba[st]
chm
cmd
com
cpl
crt
eml
exe
hlp
hta
in[fs]
isp
jse
lnk
md[be]
ms[cipt]
pcd
pif
reg
scr
sct
shs
url