They were definitely blocking connections from our server. Additionally, that IP is the shunt we put in place to work around their last block.
Aug 11 15:14:21 mxc03-zpc postfix/qmgr[416929]: 4A7081E57CD: to=<e********@******.com.au>, orig_to=<e********@waanthropologist.com>, relay=none, delay=189551, delays=189551/0.01/0/0, dsn=4.4.1, status=deferred (delivery temporarily suspended: connect to 64.68.203.25[64.68.203.25]:25: Connection timed out)