SMTP Error 550 : Failed To Add Recipient...Sender verify failed

[sobeit]

Roundcube Webmail 0.8.5

Somehow, today all emails account can not send/recieve email.
When someone sent an email from outside, he got an error report : The email account that you tried to reach does not exist..
We can not send mail from within webmail also

This is exactly what I'm getting on when sending an email :

SMTP Error (550): Failed to add recipient "recipient mail account" (Verification failed for <my email account>
Previous (cached) callout verification failure
Sender verify failed).

i have tried to disable the sender verification from exim basic editor, remove callout* files, but still no luck. We still cannot received any mail (only works on sending email from webmail).

Weird thing is, both work fine with new accounts that i have created later.