Milter-greylist

> 
> BTW, what is your deployment's scale (how many config lines, why so many threads)? Maybe size also matters? ;)
> 
> How often do you change the configs? Does the problem occur after a few reloads (i.e. may be leaks) or this can be on the first
> attempt?
> 

The configuration file contains now 75893 entries.
It is created dynamically,
and changes about once an hour.

Before applying to production there is a syntax check executed.
The production milter-greylist process never gets incorrect configuration file.

The threads are accumulated throughout hours during the night while the milter-greylist process was hanging.
The counterpart sendmail processes are all timed out.

The problem does not happen regularly after a few reloads.
Sometimes the process is up for one week or two so.
A reload finishes in about 4 - 5 seconds if the hang does not happen which is mostly the case.