Thank you again to everyone!<br>I have set <span class="q">unix_group_enable: 0&nbsp;&nbsp; and, for good measure, left<br>nsswitch.conf set to &quot;group: files&quot; instead of &quot;group: files nis&quot; <br><br>The difference in server performance is: total. I am seeing IMAP response time of 
0.1 second instead of 10 seconds - I keep looking at the log to make sure that it's still running!<br><br></span>This is going to scroll off in a few hours, but you can see exactly where I turned off the groups and the response time line went from low to invisible
<br><br><a href="http://enki.gsd.harvard.edu/cgi-bin/larrd-grapher.cgi?host=hathor.gsd.harvard.edu&amp;service=imap2&amp;graph=hourlyhttp://enki.gsd.harvard.edu/cgi-bin/larrd-grapher.cgi?host=hathor.gsd.harvard.edu&amp;service=imap2&amp;graph=hourly">
http://enki.gsd.harvard.edu/cgi-bin/larrd-grapher.cgi?host=hathor.gsd.harvard.edu&amp;service=imap2&amp;graph=hourlyhttp://enki.gsd.harvard.edu/cgi-bin/larrd-grapher.cgi?host=hathor.gsd.harvard.edu&amp;service=imap2&amp;graph=hourly
</a><br><br>Thank you all again for your help! And I agree that this should come with some kind of warning label. Maybe put something in the default imapd.conf file along the lines of:<br><br># group checking can cause performance problems; uncomment to disable if groups are not needed
<br># unix_group_enable:0<br><br><br>thanks Betsy<br>