Over the last day or two mail has at times been very slow to leave my Outlook (2007) Outbox - even tiny text mail of only a few lines. 

Between ~midday & ~3pm yesterday, it was taking multiple 'send/receive' cycles before mail actually left my Outbox.  Shortly afterwards I started getting complaints from recipients that they were receiving multiple copies of my emails (up to 5 in one case).

Situation improved later in the afternoon - most of the time!  This morning has generally been 'OK' but it still seems sluggish;  eg. just sent a small text only email that must have taken 10 - 20 secs to clear Outbox.  Does not seem right.

Does anyone know if there are problems with the mail system?

The system status page shows all clear (not that that means much, as most will be aware).