How to delete attachments?

So I've been receiving emails from Zoho saying that I have reached my storage limit. I guess this is due to attachments being included with outgoing emails which are being added to Zoho via the BCC to Dropbox feature.

How can I see these attachments for deletion? Do I seriously have to go into every individual contact and then read through every single email sent to find the ones with attachments? This will be around a million separate steps.

What if I want to keep a record of those emails, but not the attachments? Can they be deleted without removing the whole email?

And is there a way to tell BCC to Dropbox NOT to include attachments so this doesn't happen again?