only gmail allow issue

RouterOS General
1

I wanna to block all site except gmail.com from my router board(on 450g router board).Have any idea regarding this firewall issue?

2

All site, or all services?
Like gmail ok for all,
No other web sites,
Yes to DNS, NTP, POP3, SMTP, IMAP…

3

All sites must be blocked except gmail allow on private network… must be allo smtp and pop port also…