Sendmail problems on relay

Does any body have an idea why such errors come and how can they be avoided.
These kind of errors do not show up on any email sent from this server.
These errors come from emails generated with Outlook 2002 and relay from an
internal exchange server. The exchange server relays the data without
problems to the mail hub, but in the final delivery say to yahoo it gives
this  error. With some other external mail servers I often receive I/O
errors. Any idea !

The original message was received at Thu, 6 Mar 2003 09:54:10 +0100 from
mail.test.txt [192.168.3.11] with id h268s7b24079

   ----- The following addresses had permanent fatal errors -----
<[email protected]>
    (reason: 552 Put ,E=\r\n at the end of Mether, Mtcp, or Msmtp in
sendmail.cf if you are using Solaris 2.5 (fi... cannot accept messages with
stray newlines.  Many SMTP servers will time out waiting for \r\n.\r\n.)

   ----- Transcript of session follows -----
... while talking to mx1.mail.yahoo.com.:
>>> DATA
<<< 552 Put ,E=\r\n at the end of Mether, Mtcp, or Msmtp in sendmail.cf if
you are using Solaris 2.5 (fixed in 2.5.1). I cannot accept messages with
stray newlines.  Many SMTP servers will time out waiting for \r\n.\r\n. 554
5.0.0 Service unavailable



Sincerely
Mr. Olsi Lulani