"Live Mail" running on a Win 7 system on the home computer.

Two days worth of 'sent' items have gone missing!  4th to 6th January.

Might only do 3 or 4 sends per day, or even less, but one that went missing was a 'bulk mail' - a Christmas news with all recipients in the Bcc box, so as not to give recipients a list of email addresses they don't necessarily need. [Also I believe prevents hackers getting lots of addresses if one of the recipients were not well protected.]

Later that day we needed to check who had been included, and who not, but the mail was not in the 'sent' box.

It definitely went, as we have had responses from quite a few that received it.

Any clues as to why this might have happened?   Should I check for updates of Live Mail?

TIA.