Mail relay problems

[Tanya N kessler]

Can someone tell me what is going on and a possible
fix.  SMTP was working find just yesterday, no
problems and now this:

maillog.log
*****************************************************
Jan 13 23:51:14 server sendmail[4877]: a0H8uGjk337399:
ruleset=check_rcpt, arg1=<audiocollage at sbcglobal.net>,
relay=adsl-123-456-789-123.dsl.ipltin.ameritech.net
[123.456.789.123], reject=550 5.7.1
<audiocollage at sbcglobal.net>... Relaying denied
Jan 13 23:51:17 server sendmail[4877]: a0H8uGjk337399:
from=<thomaskessler at foobar.com>, size=0, class=0,
nrcpts=0, proto=ESMTP, daemon=MTA,
relay=adsl-123-456-789.dsl.ipltin.ameritech.net
[123.456.789.123]
*****************************************************

What does it all mean???
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