GFI MailEssentails AntiSpam module is designed only to listen on and scan Inbound SMTP traffic. When internal emails (sent from and to the same domain) are blocked, one of the below is true:
Email is an auto-generated notification and is sent from a server, network device or third party software.
- Email is sent from a Mobile device.
- Email is sent from an Email Client other than Microsoft Outlook and sends internal emails through SMTP rather then MAPI.
- Email is relayed through multiple Mail Servers internally, which communicate through SMTP between them.
- The same Email Domain is spread through Mail Servers physically situated in different locations and communicating outside the LAN.
- Stop SMTP or Exchange Transport Service.
- Open the GFI MailEssentials Configuration.
- Go to General Settings > Settings > Local Domains.
- Remove the domain from the list and click Apply.
- Go to the Whitelist, add the desired entries (in this case, *@domain) and then click Apply.
- Go back to Local Domains, re-add the domain and then click Apply.
- Go to Anti-spam filters > Antispoofing and enable it adding the IP address of SMTP server/s and then click Apply.
- Go to Filter Priority and make sure that Antispoofing is above whitelist.
- Restart the service stopped in step 1.
Anti-Spoofing will let pass through any internal email which has an authenticated connection with Exchange through SMTP. If the internal email makes it through Anti-Spoofing, the domain is whitelisted, so that it is not stopped by another filter.
Enabling Antispoofing is important to avoid the risk of being impersonated by spammers.