MX error in qmail. Need help badly

Anyone encountered this error? badly need help. can't receive any email. It was suddenly turns into this. This was stables a year ago and suddenly encountered this error. This is the first time I encountered this problem:


Hi. This is the qmail-send program at mcs.foo.com.
I'm afraid I wasn't able to deliver your message to the following addresses.
This is a permanent error; I've given up. Sorry it didn't work out.

<nelsonts@foo.com>:
Sorry. Although I'm listed as a best-preference MX or A for that host,
it isn't in my control/locals file, so I don't treat it as local. (#5.4.6)

I need help please while im googling