Indeed. Spam filters, porn filters, swearword filters... all of those have precedents (in mainstream, non-social/internet media) and are perfectly acceptable by most of society.
In addition, notice that even GMail doesn't actually filter spam. It just hides it - it's an assistant, not arbiter of what you should see. It's more than happy for you to adjust the filters (for yourself personally).
Edit: GMail also does prioritization as of recently - but again, the purpose of that is to help users not filter content. Again, those algorithms are also adjustable for each user separately, they just have some "smart" defaults.
>GMail doesn't actually filter spam. It just hides it
This is not accurate. There is a long on-going issue with GMail (and others) wholesale blocking delivery of email from domains/IPs/providers it deems to be spam or otherwise inappropriate. GMail users get no indication/notification, and generally have no idea that email sent to them was simply not delivered.
Kind of. You can't turn their anti-spam off, you can't exclude addresses from it and, worse for me, Gmail can hard bounce if it doesn't like something in your server/IP/content in a way that's not fully documented or reproducible.
You can now. You can create a filter matching whatever criteria you want (including from:foo@example.com or a catch all), and specify matches 'never get flagged as spam'. Its not obvious, but it is there. And the usual limitations of filters apply, such as not being able to match arbitrary headers.
That only works on mail that actually gets delivered to your mailbox. Gmail can and will:
- Reject delivery of mail from sources it has determined to be spammy (e.g. residential IPs) - this mechanism allows the sender to be aware that delivery failed.
- Accept delivery and then silently drop the message somewhere between after accepting delivery but before appearing in the end user's mailbox.
In either case, there is nothing you (the mailbox holder) can do. In the second case, there is no way for anyone to know the message hasn't been delivered.
Things can get flagged outside of your mailbox as so spammy that they will never arrive. This is how every spam filter works that I have seen to date and google is no exception.
In addition, notice that even GMail doesn't actually filter spam. It just hides it - it's an assistant, not arbiter of what you should see. It's more than happy for you to adjust the filters (for yourself personally).
Edit: GMail also does prioritization as of recently - but again, the purpose of that is to help users not filter content. Again, those algorithms are also adjustable for each user separately, they just have some "smart" defaults.