==== Required information ====
- iRedMail version: 0.8.7
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Linux/BSD distribution name and version: Ubuntu 14.04
- Related log if you're reporting an issue:

Dear Mr.Zhang,
Thanks for your previous valuable feedback. Much appreciate it.
I have difficulties understanding the syntax and rules.

What I am trying to achieve is as follows for UserA@mydomain

UserA can receive any email from anywhere.
UserA can only send e-mail within domain.

  SET \
         rejectedsenders=  \       
         allowedsenders=  '@',\
         rejectedrecipients='@.', \
         allowedrecipients='@mydomain', \
     WHERE \
          username='UserA@example.com';

Does my rule make sense above? Could I implement such rule?

Appreciate if you could provide me some feedback.

Thank you very much
Best Regards
Kevin.