[CentOS] mbox files - can they be "compacted"?

Hi All ;)

Is there an option to compact large mbox files from the shell? I did not
find anything in google, I have some very large constantly updated mbox
files and would like to know if they can be made smaller with any tool.
AFAIK mutt does such operation when for example an email is deleted but I
am curious if there are other options.

BR,
Rafal.