URGENT... deliver return status 75

[Steve Khoo]

I have a system running cyrus server 1.5.14

It's been working fine for a long time, but sendmail just started to 
queue up messages with status deferred.  It appears that deliver is 
returning status code 75.  Anyone know what this error code means? 
Where can I find a list of error code definitions?

I am able to run deliver manually with success.  I'd appreciate any help.

Thanks!

Steve