You can easily cut down the spam in Exchange 2013 (or earlier) by setting up IP Block List Providers agent. There are few Real Time Block lists that are free and easy to add. Before adding any of these please check their terms and conditions and usage guidance.
The ones that I’m using are SpamHaus – zen.spamhaus.org, SpamCop – bl.spamcop.net, Surriel – psbl.surriel.com, SORBS – dnsbl.sorbs.net
They can be easily added by typing the following into Powershell
Add-IPBlockListProvider -Name Surriel -LookupDomain psbl.surriel.org -AnyMatch $True -Enabled $True -RejectionResponse “Your IP is on the psbl.org block list“
To check which you added so far enter
Get-IPBlockListProvider
If you want to remove one of the providers enter following
Remove-IPBlockListProvider -identity <name>You can check detailed instructions about block lists here http://www.crynwr.com/spam/
To see if your lists are effective, wait a few days for traffic to accumulate and then enter following after going to your \Exchange Server\scripts folder
Get-AntispamTopRBLProviders.ps1