Does it help or hinder spam control if I empty my spam folder?

Does it help or hinder spam control if I empty my spam folder?

Most of our spam goes to the spam folder (good) but regularly I get, what to me are the same spam emails going to my inbox too (where I mark it as spam).  So, I have a common subject line and body that go to spam and yet suddenly they don't and go to inboxes.  I appreciate that polymorphic 'from addresses and subject lines' and the fact that the domain has many 'To:' addresses (aliases are also heavily used) makes life hard BUT a good implementation of Apache SpamAssassin , spamhaus SBL, XBL, PBL, PDL, spamcop IP Blocking lists, work fine for me elsewhere.

Is this a fault in the system, or something I/we are doing wrong?  Are Zoho just using white/black lists?  Does Zoho use the excellent spamhaus.org blocking lists?  Does Zoho use the spamcop.net IP block list? 

There is not even a top level help topic in Zoho Mail about spam for me to read, hence my questioning here.