[imp] problems responding to an ical invite

[liam hoekenga]

On my production webservers, when you respond to an iCal invite in IMP, you get
this error:

    Error sending reply: sendmail returned error code 64.

The mail logs show this..

Sep  6 20:29:07 mohican sendmail[7010]: j870T73e007010: setsender:
@web.mail.umich.edu: invalid or unparsable, received from www at localhost
Sep  6 20:29:07 mohican sendmail[7010]: j870T73e007010: from=www, size=1441,
class=0, nrcpts=1, msgid=<20050906202907.rlw45kgd4cw4kw8s at web.mail.umich.edu>,
relay=www at localhost

I'm guessing I've got something misconfigured.  You can otherwise send email
from the machines.  Any ideas?

Liam