imsimta purge deletes too much

does anyone know the various filenames that imsimta purge looks at?

it runs every four hours by default and thru testing, it seems one name it purges is mail.log*

... but I cannot find any documentation on what it really does purge   :-)

I had mail.log-1, mail.log-2, mail.log-3 and so forth, then the nightly mail.log_yesterday started to go away by itself at 4am ...

I see that the purge function is needed to get rid of things like

-rw-------  1 oracle oracle	1880 Mar 13 12:01 tcp_submit_slave.log-0N2D00BZLTUCX370
-rw-------  1 oracle oracle	1739 Mar 13 12:17 tcp_submit_slave.log-0N2D00BZOUL3X380