Last week I changed the way we send out email from Exchange. Previously I
had been sending directly to recipient using DNS, but due to IP blocking
issues decided to relay all email from my office thru our ISP mail server.
At first glance it appeared to work with no problem. But after a few hours,
it stops working, and the mail ends up sitting on my server in the
"unreachable destination" queue.
To set this up I added the ISP mail server in the smarthost field under the
advanced tab in the delivery section of the Default SMTP virtual server
properties. I also added our ISP username and password in the outbound
security tab on the delivery page. I then added the same smarthost to the
property pages of the Small Business SMTP Connector. All seems to work well
for a short time, then all outgoing mail stops.
Am I doing something wrong? To release the mail that gets held up all I
need to do is switch back to using DNS in the SMTP connector.