ORF DHA and Exchange 2007 - ORF Forums

@Barry George: There are no known issues with Exchange 2007 and the DHA Protection Test. This test works in quite simple way: if a single IP address attempts to send emails to recipients failing the Recipient Validation or the Recipient Blacklist test "X" times in "Y" seconds, the DHA Protection test will keep blacklisting the IP for a "Z" time.

If you check the logs, you should see preceeding attempts from 192.197.60.190 that failed either of the above tests. This can even be a single attempt if that has many non-existent/blacklisted recipients. The default DHA settings are 'Ban the sending IP for 24 hours if at least 3 invalid delivery attempts are made within 3 hours", so it is 3 hours worth of logs to be checked. If senders are frequently failing on the DHA Protection Test, please consider increasing the number of invalid delivery attempts required or decrease the attempt window of 3 hours.

@Barry George: I think slow connections do not contribute to this. If you find that the usual DHA hits are legitimate (I mean, they do catch DHA and not legitimate emails) and this issue occurs only with this specific sender, you can add the sender domain to the DHA Sender Exceptions. A typical issue would be newsletters, etc. arriving to staff that long left the company - only a few of these can trigger the DHA Protection. In this case, the best solution is to use the Recipient Exceptions and add these no longer active staff addresses.