Trac internal error

[duncan]

this is a cut and paste from my browser, after changing a ticket. This is not the first one I've got. The ticket change did occur.

Oops...
Trac detected an internal error: 
(451, '4.3.2 Please try again later', 'ole.nielsen@anu.edu.au')If you think this really should work and you can reproduce it. Then you should consider to report this problem to the Trac team. 

Go to http://trac.edgewall.com/ and create a new ticket where you describe the problem, how to reproduce it. Don't forget to include the python traceback found below. 

TracGuide — The Trac User and Administration Guide 

Python traceback
Traceback (most recent call last):
  File "/usr/lib/python2.3/site-packages/trac/core.py", line 531, in cgi_start
    real_cgi_start()
  File "/usr/lib/python2.3/site-packages/trac/core.py", line 526, in real_cgi_start
    dispatch_request(path_info, args, req, env)
  File "/usr/lib/python2.3/site-packages/trac/core.py", line 441, in dispatch_request
    module.run()
  File "/usr/lib/python2.3/site-packages/trac/Module.py", line 44, in run
    self.render()
  File "/usr/lib/python2.3/site-packages/trac/Ticket.py", line 449, in render
    self.save_changes (id)
  File "/usr/lib/python2.3/site-packages/trac/Ticket.py", line 378, in save_changes
    tn.notify(ticket, newticket=0, modtime=now)
  File "/usr/lib/python2.3/site-packages/trac/Notify.py", line 228, in notify
    NotifyEmail.notify(self, ticket['id'], subject)
  File "/usr/lib/python2.3/site-packages/trac/Notify.py", line 131, in notify
    Notify.notify(self, resid)
  File "/usr/lib/python2.3/site-packages/trac/Notify.py", line 81, in notify
    self.send(to)
  File "/usr/lib/python2.3/site-packages/trac/Notify.py", line 346, in send
    NotifyEmail.send(self, rcpt, hdrs)
  File "/usr/lib/python2.3/site-packages/trac/Notify.py", line 160, in send
    self.server.sendmail(self.from_email, rcpt, msg.as_string())
  File "/usr/lib/python2.3/smtplib.py", line 676, in sendmail
    raise SMTPSenderRefused(code, resp, from_addr)
SMTPSenderRefused: (451, '4.3.2 Please try again later', 'ole.nielsen@anu.edu.au')