Email Sending Problem (451 Temporary local problem)

[saj]

It's about 2-3 days that I can't send any email with both my 2 email accounts.
I use Outlook Express 6, set all the settings correctly and can receive messages.
I was using them with no problem (sending & receiving) but suddenly in sending it says:
The message could not be sent because one of the recipients was rejected by the server. The
rejected e-mail address was '%%%'.
Subject '%%%%', Account: '%%%%', Server: '%%%%%', Protocol: SMTP, Server Response:
'451 Temporary local problem -


Any one can help?

[chirpy]

You need to check the exim mainlog on /var/log/exim_mainlog (linux). If you're an end-user then you need to speak to your web hosting provider.