I am facing strange issue with EXIM. Whenever, I try to send mails from an email account, it doesn't get send and error is shown at attached in the OP's first post. I am facing this problem with existing email accounts. If I create a new email account and send the mails, it works fine. Already done with Exim rebuild / rewrite conf. etc. etc. but no luck. Out of idea. Could you please check and help?
Facing this problem all the existing email accounts on all the domains.
Disabling CSF doesn't help either.