I have been using Window Live Mail with no problems.

I few months ago it stopped sending  (although receiving ok) but it mysteriously started again the next day. Now I have the problem again. I have tried different ports as suggested elsewhere but they don't work. I've check port 25 ok with my ISP (BT)  by using telnet and the port isn't blocked. All mail from elsewhere is coming in ok but anything I send from WLM disappears from Outbox, goes into Sent but then doesn't arrive - I've checked this as I have 3 emails and truied sending mail between them. If I send on webmail they work ok. I have also deleted one of my accounts and re-set it up but still the same problem.