A domain is configured to allow one IP address only as the designated email sender. This is configured using an SPF entry.
When my .NET smtp client sends an email from a different IP address other than the one specified in the SPF record the message does not arrive at the recipient, as you would expect. However if I add a bcc recipient the bcc recipient does receive the email even though the IP address is not permitted to send.
Is this normal? What is the reason for this?