I use Windows Live Mail 2011.  I can send Emails OK.  Suddenly when sending Emails with attachments (usually jpg photos) my TalkTalk security set-up blocks them with message:

Attachment:  Malformed message.    E-mail blocked.            The message ends up in the SENT folder but the recipient doesn't receive it.

I notice that in the 'Subject' line in this error window it shows the subject as I've typed it, but with additional characters that I can't identify -

e.g.  "subject as typed" butterfly_top.gif[1/2].   I cannot find such a filename anywhere in my m/c although it is poss. it has been accessed sometime in the past. Might these extra characters in the Subject box be causing the problem and where are they coming from? 

If I send the same message with the same attachment using TalkTalk mail the message and attachment gets sent and received OK with no problem. 

I've been quite happy with Windows Live Mail up to now and want to continue to use all my contacts/sent/input/deleted msg folders etc. 

I'd be grateful for any advice.....

Regards         PAH75