sendmail problem

[serge%ucbcory%berkeley at sri-unix.UUCP]

From:  Serge Granik <serge%ucbcory at berkeley>

	My machines are having problems with sendmail.  The program
refuses to recognize the at sign (@).  If I try to mail to user at machine
it comes back, saying: "user at machine ... unknown user".  Any idea as
to what is going on, and how to combat this treachery?

							serge at ucbcory