[imp] imp compose sendmail error code 1

[dduncan@bushmills.cord.edu]

Hello
Occasionally our users receive an error message when clicking
on the Send Message button in the message composition window. If the
user waits for some interval and tries to send the message again, it 
will usually be successful.

This is the message the users receive: "There was an error sending
your message: sendmail returned error code 1"

This is what is logged in the horde log:

Oct 04 07:41:38 HORDE [error] [imp] sendmail returned error code 1 [on line 859 of "/usr/local/apache/htdocs/horde/imp/compose.php"]

Our environment is:
Solaris 8
sendmail 8.11.6
apache 1.3.26
horde 2.1
imp 3.1
turba 1.1
mysql 3.23.51
php 4.2.2

Any ideas on what is causing this intermittent error?

Thanks.

------------------------------------------------------------------
Dennis Duncan                   dduncan@cord.edu
Network Manager                 
Concordia College               http://www.cord.edu
Moorhead, MN 56562              Ph: 218-299-4192 FAX: 218-299-3947