I have recently installed a second hub transport server to do some testing (nothing configured at first), i noticed after a couple of hours that any emails sent via outlook were getting caught in the new hub transport server. not in any queue that could be flushed through but if i clicked on the messages tab i could see them all listed there. i had to delete them all with NDRs so they could be resent.
If i configure the new hub transport server with a send connector, or add it to an existing send connector all emails flow ok. If i shut the new hub transport server down then the emails go out the original hub transport server.
emails sent via OWA, LOB app or mobile phone all seem to go through the original hub transport server, emails via outlook all get caught in the new HT server if it's send connector isn't enabled.
i only wanted emails to go out via this HT server when the original is shutdown. Has anyone seen this before or know what causes it and how to resolve?