Need sysadmin expert for 2 issues.

Hello ,

i have 2 issue :
1 - in /var/log/mailog/
i have some bruceforce attack , i want to stop briceforce attack,

2----- want to setup mailclient (roundecube or any other mailclients )
i have already postfix installed , so i can send email perfectly

but receiving email is not possible !


please let me know if you can help me

thanks.