Enforce IP restriction in Exchange Receive connector to prevent SPAM circumnavigating Anti-SPAM.

For AVG Anti-SPAM

Enforcing IP restrictions is absolutely critical to complete protection of your mail server. Because hackers and spammers can easily bypass cloud services and target your server directly, mail servers protected by AVG AntiSpam should accept only accept SMTP connections from AVG AntiSpam IP’s listed below and deny all other traffic:  

100.42.120.96/27 (100.42.120.96/255.255.255.224)

100.42.115.0/27 (100.42.115.0/255.255.255.224)

208.70.208.0/22

1. From the EAC, click mail flow.

2. On the Mail Flow menu, click “Receive Connectors”, then select Default Hub Transport, and finally click the edit icon.