What is the proper way to clear the attachment files that don't appear to
getting removed?

I'm seeing tons of files in the /var/lib/datasysnc/mobility/attachments/o
directory on the server, I presume these are either attachments viewed on
the device or included with messages sent tothe device.

As I reset my server on Nov. 3rd and while I have only about 30 users so
far, this is taking up almost 500 Mb.