looking for spam/virus protection in connection with exchange 2013/2016 for smaller organisations

Hello, 

I am looking for good spam/virus protection for organisations below 100 Mailboxes.

What can you recomend?

Currently there is a mixed receive modus means  POP3 Port 110 for  @domain1.com   and  SMTP Port 25   for @domain2.com

thx in advance