3 times now Mailman has stopped sending mail, system wide. several lists on several domains on the same server although different IP addresses.

Anyone know what causes this? Is it a common problem?

The last time they removed the list name from the locks directory and it started working, I see it is gone again but still not working. I tried to remove it myself but the rm command didn't work but I may not really know how I am not used to woking at that level with linux commmands

Raymond