All of a sudden I am getting the error:

Last error: 5.1.1 550 5.7.1 Relaying not permitted

for over 100 susbcribers to my listserv.

Never having gotten this error before with so many susbcribers, I am concerned that something is
awry. I have not done anything to change my list (no header changes that is) and the accounts
sending this error back to listserv are varied and not from new subscribers.

Any ideas? SHould I be concerned?

John Mack