Just in case it might be useful to someone else, here's my experience with an internal server error.

I had installed Sugar OS and was trying it out. Trying to send an email produced an internal server error. Prior to installing Sugar, I had to enable PHP5 in a .htaccess file with the following line:

Code:
AddHandler application/x-httpd-php5 .php
I checked this file, and this is what it looked like this after the Sugar additions from installing:

Code:
AddHandler application/x-httpd-php5 .php# BEGIN SUGARCRM RESTRICTIONS
RedirectMatch /sugar/sugarcrm.log.* http://z411.com/sugar/log_file_restricted.html
RedirectMatch /sugar/emailman.log http://z411.com/sugar/log_file_restricted.html
RedirectMatch /sugar/not_imported_(.*).txt http://z411.com/sugar/log_file_restricted.html
RedirectMatch /sugar/XTemplate/(.*)/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/data/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/examples/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/include/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/include/(.*)/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/log4php/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/log4php/(.*)/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/metadata/(.*)/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/modules/(.*)/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/soap/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/emailmandelivery.php http://z411.com/sugar/index.php
# END SUGARCRM RESTRICTIONS
I inserted a carriage return to move the Sugar additions to the next line, like this:

Code:
AddHandler application/x-httpd-php5 .php
# BEGIN SUGARCRM RESTRICTIONS
RedirectMatch /sugar/sugarcrm.log.* http://z411.com/sugar/log_file_restricted.html
RedirectMatch /sugar/emailman.log http://z411.com/sugar/log_file_restricted.html
RedirectMatch /sugar/not_imported_(.*).txt http://z411.com/sugar/log_file_restricted.html
RedirectMatch /sugar/XTemplate/(.*)/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/data/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/examples/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/include/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/include/(.*)/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/log4php/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/log4php/(.*)/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/metadata/(.*)/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/modules/(.*)/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/soap/(.*).php http://z411.com/sugar/index.php
RedirectMatch /sugar/emailmandelivery.php http://z411.com/sugar/index.php
# END SUGARCRM RESTRICTIONS
Then I tried to send the email again, and it worked. :-)