Are you finding those messages in the UceArchive folder?
– Take a look at message headers – is it originating from an IP address that has been added to the Global Accept List?
– Is that IP address on the internal SMTP servers list as well? (The same IP address should not exist on both these lists).
– Is Connection Filtering enabled on the SMTP Virtual Server?
One way to get around this is to create an additional SMTP Virtual Server using a different IP address (you may need to add one to the network card’s TCP/IP configuration first), and not enable antispam filters on it, including IMF. You can restrict connections to that SMTP VS only to trusted/internal IP addresses.
You can also enable/disable filters for different IP addresses that a SMTP VS is bound to. In other words, if a SMTP VS is listening on more than 1 sockets (unique combination of IP address + port), you can have filtering enabled on one, and disabled on the other one.