Where are my emails going?

I'm using Windows XP and Outlook 2003.

I have five different email addresses, which all download straight into Outlook.

When my emails download I get a little notification down near the taskbar which tells me something like, "receiving message 8 of 12" as each different email address is checked and the messages download.

I've recently noticed that the numbers don't tally with what actually appears in Outlook. I've checked it a few times now. Only a small proportion of those messages seem to get through.

I have added quite a lot of email addresses to my junk senders list, so all those end up in my Junk Mail folder; but even accounting for those, I still seem to be missing an awful lot of messages. This morning a total of 45 messages downloaded into Outlook: but I could find only 16 new items in my Inbox and Junk Mail combined. They didn't end up in Deleted Items, as I checked there; and I don't have any rules set up to filter them into different folders.

Have I done something foolish? That's always possible. Is there a reasonable explanation for this? Or has my computer turned into The Great Acer Chasm Where Emails Are Lost For Ever?

Yep, I checked EVERYWHERE. I hoped they'd be tucked away somewhere else, but they're not.

Medie, my mail comes in on a POP3 thingummy-wotsit. I'm using Outlook because I'm used to it, and I haven't got on with web-based email thingies when I've tried them (I much prefer having everything on my computer--far quicker when I was on still dial-up, which was only a couple of weeks ago). What else would you suggest? I mostly do as I'm told when it comes to computing advice from clever women.

And Carl, nope, it's not going into my junk folder or anywhere else, and I don't have any filters set up so that can't be it.