[Mailman-Users] Slows down takes days to send the mail.

Does anyone have any ideas why all of my mailman mailing lists have slowed down and takes days for them to send the mail out ?

I have several on two different domains and they have all slowed down. At last check it was taking 3 to 4 days for them to send the mail. I have a feeling it may be taking longer now.

...Bryon