Mailman only sending to some members

[draggle]

Mailman version 2.1.9.cp1 is only sendingmail to some members, not others.

I have all filters turned off (caused too many problems with blank body emails being sent to the list).

I don't know how extensive the problem is, but I know for sure it is happening. I have 2 of my own email addresses subscribed, and neither of them received a recent email I myself sent to the list. Imagine my surprise when the list circulated a reply to my email from a list member who had received it....

Can anyone point me in the direction of a solution?

Or even where to look for a diagnosis?

Oh, and I'm a raving newbie.

Thanks
Drag the Barrel