451 Temporary local – PHP Mailer

I am using phpmailer to do may emailing in the website, using SMTP auth. However recently i noticed that i gives me a error,

SMTP Error: The following recipients failed: info@xxx.com 

Then i turned the debug variable to true in the mailer class, i got following as the output basically saying its a temporary problem and try again later, may i know what should i do to solve this problem ?

SMTP -> get_lines(): $data was ""
SMTP -> get_lines(): $str is "220-servername ESMTP Exim 4.77 #2 Wed, 25 Jul 2012 08:59:03 +0530 "
SMTP -> FROM SERVER:220-servername ESMTP Exim 4.77 #2 Wed, 25 Jul 2012 08:59:03 +0530 220-We do not authorize the use of this system to transport unsolicited, 220 and/or bulk e-mail.
SMTP -> get_lines(): $data was ""
SMTP -> get_lines(): $str is "250-servername Hello xxx.com [199.xxxx.185] "
SMTP -> get_lines(): $data was ""
SMTP -> get_lines(): $str is "334 VXNlcm5hbWU6 "
SMTP -> get_lines(): $data is "334 VXNlcm5hbWU6 "
SMTP -> get_lines(): $data was ""
SMTP -> get_lines(): $str is "334 UGFzc3dvcmQ6 "
SMTP -> get_lines(): $data is "334 UGFzc3dvcmQ6 "
SMTP -> get_lines(): $data was ""
SMTP -> get_lines(): $str is "235 Authentication succeeded "
SMTP -> get_lines(): $data is "235 Authentication succeeded "
SMTP -> get_lines(): $data was ""
SMTP -> get_lines(): $str is "250 OK "
SMTP -> get_lines(): $data is "250 OK "
SMTP -> FROM SERVER:250 OK
SMTP -> get_lines(): $data was ""
SMTP -> get_lines(): $str is "451 Temporary local problem - please try later "
SMTP -> get_lines(): $data is "451 Temporary local problem - please try later "
SMTP -> FROM SERVER:451 Temporary local problem - please try later
SMTP -> ERROR: RCPT not accepted from server: 451 Temporary local problem - please try later
SMTP Error: The following recipients failed: info@xxx.com