I have been running Postfix 2.6.6 for the last 5 months. There has not been any server changes and the config allowed me to send 150,000 emails per hour with no problems.
Now, things have slowed down and are progressively getting slower since about a week ago.
The snapshot I linked shows my "delays" and you can see that the "Time in Queue Manager" has gone to 3 and 4 seconds which has choked my mail delivery down to about 20,000 mails per hour vs 150,000.
Does something need to be flushed or reset somewhere? I don't understand why, with no changes, that all of a sudden I begin to get these large delays after working beautifully for several months.