I did 'something' to our sbs 2011 / exchange 2010 server and now incoming mail bounces after getting to our spam filtering service with this message:
Connected to [x.y.z.a] but recipient was rejected. STARTTLS proto=TLSv1; cipher=DHE-RSA-AES256-SHA.
Remote host said: 550 (result of an earlier callout reused).
the remote host is the exchange server I guess?
never heard of that result of an earlier callout reused message and google is not much help at all.
we get that bounce back when sending from different domains that worked earlier and gmail accounts