Transport rule to send Bcc to mailbox when sender is from particular external mail domain?

Hi,

is there a way to create a transport rule to send Blind carbon copy (Bcc) of email when the sender is from particular external mail domain? (i.e.: when sender isuser@ext.domain.com, send Bcc to ext.domain@int.domain.com mailbox)

Thanks.

(I have created a rule to send Bcc to ext.domain@int.domain.com mailbox when the recipient's address contains "ext.domain.com", but I can't find the way to do this for ext.domain.com senders.)