mail server problem
 

I try to setup my mail server (Qmail).Suppose it's name is mail.example.com.I create localuser in this server user1.I set mx record of domain example.com in dns point to mail.example.com with preference value=10.when I send mail from my gmail account.I send to user1@example.com but It 's rejected so I try again with user1@mail.example.com.It 's work properly.Who can explain why I have to specify name of mail server in the address?It should know my mailserver by query from dns mx record.I want to make it work for user1@example.com
How can I fix it?

Put you domain in /var/qmail/control/rcpthosts (you can also put it in /var/qmail/control/defaultdomain) and restart qmail.

Regards