ezmlm-idx>=0.32 comes with much improved bounce handling. Modification as described below should be considered only when you expect thousands of bouncing addresses (virtually never). The description remains, for users of ezmlm-0.53 or earlier versions of ezmlm-idx. For users of ezmlm-0.53 alone, we recommend a patch (FIXME ftp://ftp.id.wustl.edu/pub/patches/ezmlm-return.diff which fixes a bug in ezmlm-0.53 bounce handling. The patch is superseded by ezmlm-idx.
To redistribute the load of bounce warning and probe addresses to off-peak hours, you may want to set up the list without ezmlm-warn(1) by using the ezmlm-make -w switch, and instead execute ezmlm-warn DIR via crond(8). You also need to run ezmlm-warn -d DIR for digest bounces if your list is configured with digests. Normal ezmlm list with ezmlm-idx>=0.32 will have an insignificant bounce load, except if you bulk add addresses, e.g. from a MLM without bounce handling. In the latter case, the load will be higher for the first 2-4 weeks, then decrease drastically. If you feel you need to run ezmlm-warn(1) from crond(8), you should seriously consider sublisting your lists.
Note: the ezmlm-make(1) -w switch has a special meaning if used at the same time as enabling SQL-support (-6; see man pages).