This is just a thought, but to me the problem with emails and spam is that people who use email might only have a single email address that they use, or give out; this, as you know is very much open to being abused etc. So, how does a solid POD fix that? well, basically when you give out your email address you would also give out an email “permission”, that permission would simply be a guid that identified the site/person/company etc who wants to email you; then if the Solid POD server checked incoming emails against my user list of “permissions”, only current and approved emails would be allowed. The user would also have the option to “revoke” the “permission” on any site/person/company, thus stopping any unwanted email. If you think about it, some people already try to do something similar to this, as they might have an old email address they use for catching spam. Or they might create a new email because they get too much spam.
You might ask, but how would this work in practice; now if you imagine as per my other post on a browser-linked-pod, there could be some native JS call for a site to ask permission for a POD email address and perhaps popup a native browser ui like. “The site XYZ is asking for permission to email you?” then after clicking ok, the site email form is automatically filled in with your info etc
can it also stop all the wads of glossy paper in my physical mailbox?
not to be a party-pooper, but: The feature that makes email so useful is that everyone can send you one. One wants others to be able to contact - if I only want to talk with pre-approved persons, I can easily tell most email programs and filters to simply delete all emails from people not in my address book, which would achieve exactly what you are describing.
But the problem with spam is that you want to receive potential messages from until then unknown persons, but only if they don’t fit the spam patterns, which are always shifting.
So, long answer short: I don’t think that Solid Pods are a good way to stop spam. 
But I could love a Solid based email client. Instead of having the mails on an IMAP based email server, have them stored on the Solid pod and interact with them via a Solid webclient.
Hi JollyOrc, The process flow would allow for people to email you directly; the big difference is, you decide if they have to be human or not, you decide if they have to do a captcha or count cats in a series of images etc etc; If the Solid email client detects spam and removes that “permission” the spammer would no longer have your contact email address; how now can they send spam to an email box that doesn’t exist. This way a default higher level of protection can be setup around the more vulnerable users.
Thoughts?
That doesn’t sound very interoperable with current email clients though.