Возможно, suexec (переключают пользовательское должностное лицо), то, что Вы ищете.
документ человечности http://manpages.ubuntu.com/manpages/lucid/man8/suexec.8.html
апачский документ http://httpd.apache.org/docs/current/suexec.html
No, you're wrong.
Send-As
and existing calendaring entries often "break" with a mail migration. Depending on the details of your setup and migration, this may be fixable or worked-around, or it may not be. Either way, this type of issue is definitely "normal" with a mail migration.