I switched to queued delivery. The emails were generated into the app/spool dir. (>10k)
However with each spoolfile being more than 50k it took almost 1GB of space.
I plan to send even larger segments. With that the amount of space required to temporarily store spool files can go up to multiple of 10GBs
A simple gzip compression would not use much cpu, while it would lower the needed space significantly.
Could someone please make it happen?