> [I] set "TUNE_MANY_LISTS=1" and restarted, holding my breath. 
> Whew!  That seems to have solved the problem.  Yay!  Was this variable around last September when tried 1.8e?

There have been many performance improvements in the level set for HPO sites with many lists. These improvements do not correct slowdowns introduced in 1.8e, the same performance issues were present in 1.8d. But the addition of the Subscriber's Corner to 1.8e has led to a significantly higher level of many-list queries since they have become so much easier for the end users. Initially, some sites chose to disable the Subscriber's Corner when the hardware was already near its limit.

The 1.8e web interface (including templates) will not work to 100% with 1.8d. In addition, it will work more slowly with 1.8d than with 1.8e. Setting aside any specific issues there might be with AIX 4.3, the 1.8e lsv is generally faster than 1.8d, other than in a very small number of areas where the difference in performance is due to adding necessary processing that 1.8d should have done, but did not (ie bugs). This is mostly in the mail-merge code for DISTRIBUTE. One thing that could be interesting to try is the 1.8d web interface with the 1.8e lsv.

I do not know why your SMTP workers cannot cope with the workload under 1.8e, but I would look at the system's overall performance. Is the MTA able to take in the messages? Something is wrong if you need 19 workers to deal out 250k daily deliveries! Perhaps there are old or corrupted .mail files in the spool with invalid SMTP sequences that slow down everything. I would also look at swapping and CPU utilization. New versions generally consume a bit more memory, and in the case of wa this could be significant as there can be many copies of wa running concurrently. Note also that TUNE_MANY_LISTS=1 consumes additional memory.

  Eric