It is interesting how your AntiSpam filters installed in exchange 2007 HUB servers will start to block connections when the Sender ID filter is enabled.
This can happen if you have a front end SMTP servers (SMTP Relays) in front of your HUB servers .When an RFC-compliant SMTP server receives a message, the server updates the message’s Received header with the domain name and IP address of the sender. Therefore, for each SMTP server that is between the originating sender and the Hub Transport server, the SMTP server adds an additional Received header entry.
This means that your SPF check will fail because the IP addresses of YOUR SMPT Relay servers will be included in the message headers of the received message.You can overcome this by using the InternalSMTPServers switch.
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