Bull! It is a limitation of neither Linux nor Sendmail, as the simple
change to the aliases file (which is merely a configuration file used by
Sendmail) illustrates. It is, in fact, a limitation of the Cobalt GUI.
If you edit the file directly or use other web-based control programs
like Webmin or CPanel, you just don't have this problem. Moreover, if
you fix the problem by editing the aliases file by any means, your
efforts will be eradicated when you next use the Cobalt GUI to add a
user or adjust any user mail setting that causes the alias file to be
rewritten.